diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
new file mode 100644
index 0000000..34b56ec
--- /dev/null
+++ b/.github/workflows/run-tests.yml
@@ -0,0 +1,45 @@
+name: run-tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: true
+      matrix:
+        os: [ubuntu-latest]
+        php: [8.1]
+        stability: [prefer-lowest, prefer-stable]
+
+    name: P${{ matrix.php }} - ${{ matrix.stability }} - ${{ matrix.os }}
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          extensions: dom, curl, libxml, mbstring, zip, pcntl, pdo, sqlite, pdo_sqlite, bcmath, soap, intl, gd, exif, iconv, imagick, fileinfo, json
+          coverage: none
+
+      - name: Install plantuml & graphviz
+        run: sudo apt-get install -y plantuml graphviz
+
+      - name: Setup problem matchers
+        run: |
+          echo "::add-matcher::${{ runner.tool_cache }}/php.json"
+          echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+      - name: Install dependencies
+        run: |
+          composer update --${{ matrix.stability }} --prefer-dist --no-interaction
+
+      - name: Execute tests
+        run: make test
diff --git a/.travis.yml b/.travis.yml
index 84851bb..2aa6d18 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,9 +6,7 @@ os:
 dist: "bionic"
 
 php:
-    - "7.4"
-    - "7.3"
-    - "7.2"
+    - "8.1"
 
 install:
     - "mkdir -p build/logs"
diff --git a/Dockerfile b/Dockerfile
index 476b411..dd96609 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM php:7.3-cli
+FROM php:8.1-cli
 RUN mkdir -p /usr/share/man/man1 \
     && apt-get update && apt-get install -y \
         default-jdk \
@@ -7,8 +7,11 @@ RUN mkdir -p /usr/share/man/man1 \
     && apt-get install -y \
         graphviz \
         plantuml
+
 COPY . /dephpend
 WORKDIR /dephpend
+
 RUN curl https://raw.githubusercontent.com/composer/getcomposer.org/76a7060ccb93902cd7576b67264ad91c8a2700e2/web/installer | php -- --quiet \
     && php -n composer.phar install
-ENTRYPOINT [ "php", "-n", "-d memory_limit=-1", "./bin/dephpend" ]
+
+ENTRYPOINT [ "php", "-n", "-d", "memory_limit=-1", "./bin/dephpend" ]
diff --git a/Makefile b/Makefile
index 083ca58..9cec68a 100644
--- a/Makefile
+++ b/Makefile
@@ -44,8 +44,8 @@ cov:
 
 s: style
 style:
-	@$(PHP_NO_INI) vendor/bin/php-cs-fixer fix --level=psr2 --verbose src
-	@$(PHP_NO_INI) vendor/bin/php-cs-fixer fix --level=psr2 --verbose tests
+	@$(PHP_NO_INI) vendor/bin/php-cs-fixer fix --rules=@PSR12 --verbose src
+	@$(PHP_NO_INI) vendor/bin/php-cs-fixer fix --rules=@PSR12 --verbose tests
 
 phar:
 	@php composer.phar update --no-dev
diff --git a/composer.json b/composer.json
index 86228f0..131b5e9 100644
--- a/composer.json
+++ b/composer.json
@@ -10,10 +10,10 @@
     "homepage": "https://dephpend.com",
     "bin": ["bin/dephpend", "bin/php-trace"],
     "require": {
-        "php": "^7.2",
+        "php": "^8.1",
         "nikic/php-parser": "^4.0",
-        "symfony/console": "^4 || ^5",
-        "symfony/event-dispatcher": "^4 || ^5"
+        "symfony/console": "^6",
+        "symfony/event-dispatcher": "^6"
     },
     "suggest": {
         "ext-json": "*",
@@ -21,10 +21,10 @@
         "ext-tokenizer": "*"
     },
     "require-dev": {
-        "mikey179/vfsstream": "^1.6",
-        "phpunit/phpunit": "^8.0",
-        "squizlabs/php_codesniffer": "^3.3",
-        "friendsofphp/php-cs-fixer": "^2.12"
+        "mikey179/vfsstream": "^1.6.11",
+        "phpunit/phpunit": "^9.5.24",
+        "squizlabs/php_codesniffer": "^3.7",
+        "friendsofphp/php-cs-fixer": "^3.11"
     },
     "minimum-stability": "stable",
     "prefer-stable": true,
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index ced3748..96a196d 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -4,7 +4,6 @@
          beStrictAboutTestsThatDoNotTestAnything="true"
          beStrictAboutOutputDuringTests="true"
          beStrictAboutTodoAnnotatedTests="true"
-         forceCoversAnnotation="true"
          colors="true"
          verbose="true">
     <testsuite name="tests">
diff --git a/src/Analyser/DependencyInspectionVisitor.php b/src/Analyser/DependencyInspectionVisitor.php
index f6b50b0..fd67b8f 100644
--- a/src/Analyser/DependencyInspectionVisitor.php
+++ b/src/Analyser/DependencyInspectionVisitor.php
@@ -153,7 +153,7 @@ public function beforeTraverse(array $nodes)
     /**
      * @return DependencyMap
      */
-    public function dependencies() : DependencyMap
+    public function dependencies(): DependencyMap
     {
         return $this->dependencies;
     }
@@ -173,6 +173,9 @@ private function setCurrentClass(ClassLikeNode $node)
         } elseif ($node instanceof TraitNode) {
             // @codeCoverageIgnoreEnd
             $this->currentClass = $this->dependencyFactory->createTraitFromStringArray($node->namespacedName->parts);
+        } elseif ($node instanceof Node\Stmt\Enum_) {
+            // @codeCoverageIgnoreEnd
+            $this->currentClass = $this->dependencyFactory->createEnumFromStringArray($node->namespacedName->parts);
         } else {
             $this->currentClass = $node->isAbstract()
                 ? $this->dependencyFactory->createAbstractClazzFromStringArray($node->namespacedName->parts)
diff --git a/src/Analyser/Metrics.php b/src/Analyser/Metrics.php
index 332649e..81e5060 100644
--- a/src/Analyser/Metrics.php
+++ b/src/Analyser/Metrics.php
@@ -18,7 +18,7 @@ class Metrics
      *
      * @return float Value from 0 (completely concrete) to 1 (completely abstract)
      */
-    public function abstractness(DependencyMap $map) : float
+    public function abstractness(DependencyMap $map): float
     {
         $abstractions = $this->abstractClassCount($map)
             + $this->interfaceCount($map)
@@ -30,28 +30,28 @@ public function abstractness(DependencyMap $map) : float
         return $abstractions / $allClasses;
     }
 
-    public function classCount(DependencyMap $map) : int
+    public function classCount(DependencyMap $map): int
     {
         return $this->countFilteredItems($map, function (Dependency $dependency) {
             return $dependency instanceof Clazz;
         });
     }
 
-    public function abstractClassCount(DependencyMap $map) : int
+    public function abstractClassCount(DependencyMap $map): int
     {
         return $this->countFilteredItems($map, function (Dependency $dependency) {
             return $dependency instanceof AbstractClazz;
         });
     }
 
-    public function interfaceCount(DependencyMap $map) : int
+    public function interfaceCount(DependencyMap $map): int
     {
         return $this->countFilteredItems($map, function (Dependency $dependency) {
             return $dependency instanceof Interfaze;
         });
     }
 
-    public function traitCount(DependencyMap $map) : int
+    public function traitCount(DependencyMap $map): int
     {
         return $this->countFilteredItems($map, function (Dependency $dependency) {
             return $dependency instanceof Trait_;
@@ -65,7 +65,7 @@ public function traitCount(DependencyMap $map) : int
      *
      * @return array
      */
-    public function afferentCoupling(DependencyMap $map) : array
+    public function afferentCoupling(DependencyMap $map): array
     {
         return $map->fromDependencies()->reduce([], function (array $afferent, Dependency $from) use ($map) {
             $afferent[$from->toString()] = $map->reduce(
@@ -87,7 +87,7 @@ function (int $count, Dependency $fromOther, Dependency $to) use ($from): int {
      *
      * @return array
      */
-    public function efferentCoupling(DependencyMap $map) : array
+    public function efferentCoupling(DependencyMap $map): array
     {
         return $map->reduce([], function (array $efferent, Dependency $from, Dependency $to) use ($map) {
             $efferent[$from->toString()] = $map->get($from)->count();
@@ -102,7 +102,7 @@ public function efferentCoupling(DependencyMap $map) : array
      *
      * @return array Key: Class Value: Range from 0 (completely stable) to 1 (completely unstable)
      */
-    public function instability(DependencyMap $map) : array
+    public function instability(DependencyMap $map): array
     {
         $ce = $this->efferentCoupling($map);
         $ca = $this->afferentCoupling($map);
diff --git a/src/Analyser/Parser.php b/src/Analyser/Parser.php
index 36c2a71..a2da813 100644
--- a/src/Analyser/Parser.php
+++ b/src/Analyser/Parser.php
@@ -1,8 +1,10 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Mihaeu\PhpDependencies\Analyser;
 
 interface Parser
 {
-    public function parse(string $code) : array;
+    public function parse(string $code): array;
 }
diff --git a/src/Analyser/StaticAnalyser.php b/src/Analyser/StaticAnalyser.php
index 47e67f9..67005e2 100644
--- a/src/Analyser/StaticAnalyser.php
+++ b/src/Analyser/StaticAnalyser.php
@@ -41,7 +41,7 @@ public function __construct(
         $this->parser = $parser;
     }
 
-    public function analyse(PhpFileSet $files) : DependencyMap
+    public function analyse(PhpFileSet $files): DependencyMap
     {
         $files->each(function (PhpFile $file) {
             try {
diff --git a/src/Analyser/XDebugFunctionTraceAnalyser.php b/src/Analyser/XDebugFunctionTraceAnalyser.php
index d00e98b..19fa54d 100644
--- a/src/Analyser/XDebugFunctionTraceAnalyser.php
+++ b/src/Analyser/XDebugFunctionTraceAnalyser.php
@@ -14,8 +14,8 @@
  */
 class XDebugFunctionTraceAnalyser
 {
-    const PARAMETER_START_INDEX = 11;
-    const FUNCTION_NAME_INDEX = 5;
+    public const PARAMETER_START_INDEX = 11;
+    public const FUNCTION_NAME_INDEX = 5;
 
     /** @var DependencyFactory */
     private $dependencyFactory;
@@ -28,9 +28,9 @@ public function __construct(DependencyFactory $dependencyFactory)
         $this->dependencyFactory = $dependencyFactory;
     }
 
-    public function analyse(\SplFileInfo $file) : DependencyMap
+    public function analyse(\SplFileInfo $file): DependencyMap
     {
-        $fileHandle = @fopen($file->getPathname(), 'r');
+        $fileHandle = !empty($file->getPathname()) ? @fopen($file->getPathname(), 'r') : false;
         if (!$fileHandle) {
             throw new \InvalidArgumentException('Unable to open trace file for reading');
         }
@@ -45,7 +45,7 @@ public function analyse(\SplFileInfo $file) : DependencyMap
         return $dependencies;
     }
 
-    private function extractDependenciesFromLine(DependencyMap $dependencies, string $line) : DependencyMap
+    private function extractDependenciesFromLine(DependencyMap $dependencies, string $line): DependencyMap
     {
         $tokens = $this->extractFields($line);
         if ($this->isNotMethodEntryTrace($tokens)
@@ -59,35 +59,35 @@ private function extractDependenciesFromLine(DependencyMap $dependencies, string
         );
     }
 
-    private function isNotMethodEntryTrace(array $tokens) : bool
+    private function isNotMethodEntryTrace(array $tokens): bool
     {
         return count($tokens) <= self::PARAMETER_START_INDEX;
     }
 
-    private function extractFields(string $line) : array
+    private function extractFields(string $line): array
     {
         return explode("\t", str_replace("\n", '', $line));
     }
 
-    private function containsOnlyScalarValues(array $tokens) : bool
+    private function containsOnlyScalarValues(array $tokens): bool
     {
         return strpos(implode('', array_slice($tokens, self::PARAMETER_START_INDEX)), 'class ') === false;
     }
 
-    private function isGlobalFunction(array $tokens) : bool
+    private function isGlobalFunction(array $tokens): bool
     {
         return strpos($tokens[self::FUNCTION_NAME_INDEX], '->') === false
             && strpos($tokens[self::FUNCTION_NAME_INDEX], '::') === false;
     }
 
-    private function extractFromClass(array $tokens) : Clazz
+    private function extractFromClass(array $tokens): Clazz
     {
         $classWithoutMethod = preg_split('/(->)|(::)/', $tokens[self::FUNCTION_NAME_INDEX]);
         $classParts = explode("\\", $classWithoutMethod[0]);
         return $this->dependencyFactory->createClazzFromStringArray($classParts);
     }
 
-    private function extractToSet(array $tokens) : DependencySet
+    private function extractToSet(array $tokens): DependencySet
     {
         return array_reduce(array_slice($tokens, self::PARAMETER_START_INDEX), function (DependencySet $set, string $token) {
             if (strpos($token, 'class') === false) {
diff --git a/src/Cli/Application.php b/src/Cli/Application.php
index 29a66e4..99cf740 100644
--- a/src/Cli/Application.php
+++ b/src/Cli/Application.php
@@ -12,7 +12,7 @@
 
 class Application extends \Symfony\Component\Console\Application
 {
-    const XDEBUG_WARNING = 'You are running dePHPend with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug';
+    public const XDEBUG_WARNING = 'You are running dePHPend with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug';
 
     /** @var ErrorOutput */
     private $errorOutput;
diff --git a/src/Cli/ErrorOutput.php b/src/Cli/ErrorOutput.php
index d5ba62c..b612a51 100644
--- a/src/Cli/ErrorOutput.php
+++ b/src/Cli/ErrorOutput.php
@@ -20,4 +20,4 @@ public function writeln(string $message): void
     {
         $this->symfonyStyle->getErrorStyle()->writeln($message);
     }
-}
\ No newline at end of file
+}
diff --git a/src/Cli/MetricsCommand.php b/src/Cli/MetricsCommand.php
index fbdf38e..d52ffdc 100644
--- a/src/Cli/MetricsCommand.php
+++ b/src/Cli/MetricsCommand.php
@@ -58,7 +58,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
         return 0;
     }
 
-    private function combineMetrics(array $afferentCoupling, array $efferentCoupling, array $instability) : array
+    private function combineMetrics(array $afferentCoupling, array $efferentCoupling, array $instability): array
     {
         $result = [];
         foreach ($afferentCoupling as $className => $afferentCouplingValue) {
diff --git a/src/Cli/TestFeaturesCommand.php b/src/Cli/TestFeaturesCommand.php
index 6235ab3..6c388cb 100644
--- a/src/Cli/TestFeaturesCommand.php
+++ b/src/Cli/TestFeaturesCommand.php
@@ -46,7 +46,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
         return 0;
     }
 
-    public function runTest(string $filename) : array
+    public function runTest(string $filename): array
     {
         $_SERVER['argv'] = [0, 'text', $filename];
         $application = new Application('', '', (new DependencyContainer([]))->dispatcher());
@@ -61,7 +61,7 @@ public function runTest(string $filename) : array
             : [false, '<error>[✗] '.$this->extractFeatureName($filename).'<error>'];
     }
 
-    private function cleanOutput(string $output) : string
+    private function cleanOutput(string $output): string
     {
         return trim(str_replace(Application::XDEBUG_WARNING, '', $output));
     }
@@ -71,7 +71,7 @@ private function cleanOutput(string $output) : string
      *
      * @return string
      */
-    private function extractFeatureName(string $filename) : string
+    private function extractFeatureName(string $filename): string
     {
         preg_match_all('/((?:^|[A-Z])[a-z0-9]+)/', $filename, $matches);
         return str_replace(['cli', ' feature'], '', strtolower(implode(' ', $matches[1])));
@@ -82,7 +82,7 @@ private function extractFeatureName(string $filename) : string
      *
      * @return string
      */
-    private function getExpectations(string $filename) : string
+    private function getExpectations(string $filename): string
     {
         $expectations = [];
         foreach (file($filename, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES) as $line) {
@@ -98,7 +98,7 @@ private function getExpectations(string $filename) : string
      *
      * @return \RegexIterator
      */
-    protected function fetchAllFeatureTests() : \RegexIterator
+    protected function fetchAllFeatureTests(): \RegexIterator
     {
         return new \RegexIterator(
             new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator(__DIR__ . '/../../tests/samples')),
@@ -112,14 +112,14 @@ protected function fetchAllFeatureTests() : \RegexIterator
      *
      * @return array
      */
-    protected function runAllTests($files) : array
+    protected function runAllTests($files): array
     {
         return array_map(function ($filename) {
             return $this->runTest($filename[0]);
         }, iterator_to_array($files));
     }
 
-    private function sortSuccessFirst() : \Closure
+    private function sortSuccessFirst(): \Closure
     {
         return function (array $x, array $y) {
             if ($x[0] === true) {
diff --git a/src/Dependencies/ClazzLike.php b/src/Dependencies/ClazzLike.php
index bf83b93..0c8ea89 100644
--- a/src/Dependencies/ClazzLike.php
+++ b/src/Dependencies/ClazzLike.php
@@ -27,46 +27,46 @@ public function __construct(string $name, Namespaze $clazzNamespace = null)
         $this->namespaze = $clazzNamespace;
     }
 
-    public function equals(Dependency $other) : bool
+    public function equals(Dependency $other): bool
     {
         return $this->toString() === $other->toString();
     }
 
-    public function toString() : string
+    public function toString(): string
     {
         return $this->hasNamespace()
             ? $this->namespaze.'\\'.$this->name
             : $this->name;
     }
 
-    public function __toString() : string
+    public function __toString(): string
     {
         return $this->toString();
     }
 
-    public function namespaze() : Namespaze
+    public function namespaze(): Namespaze
     {
         return $this->namespaze;
     }
 
-    public function hasNamespace() : bool
+    public function hasNamespace(): bool
     {
         return $this->namespaze->toString() !== '';
     }
 
-    public function count() : int
+    public function count(): int
     {
         return 1 + $this->namespaze->count();
     }
 
-    public function reduceToDepth(int $maxDepth) : Dependency
+    public function reduceToDepth(int $maxDepth): Dependency
     {
         return $this->count() <= $maxDepth || $maxDepth === 0
             ? $this
             : $this->namespaze->reduceToDepth($maxDepth);
     }
 
-    public function reduceDepthFromLeftBy(int $reduction) : Dependency
+    public function reduceDepthFromLeftBy(int $reduction): Dependency
     {
         return $this->count() <= $reduction || $reduction === 0
             ? $this
@@ -85,12 +85,12 @@ private function ensureClassNameIsValid(string $name)
         }
     }
 
-    public function inNamespaze(Namespaze $other) : bool
+    public function inNamespaze(Namespaze $other): bool
     {
         return $this->namespaze->inNamespaze($other);
     }
 
-    public function isNamespaced() : bool
+    public function isNamespaced(): bool
     {
         return $this->namespaze->count() > 0;
     }
diff --git a/src/Dependencies/Dependency.php b/src/Dependencies/Dependency.php
index 4dba315..1305025 100644
--- a/src/Dependencies/Dependency.php
+++ b/src/Dependencies/Dependency.php
@@ -6,19 +6,19 @@
 
 interface Dependency extends \Countable
 {
-    public function reduceToDepth(int $maxDepth) : Dependency;
+    public function reduceToDepth(int $maxDepth): Dependency;
 
-    public function reduceDepthFromLeftBy(int $reduction) : Dependency;
+    public function reduceDepthFromLeftBy(int $reduction): Dependency;
 
-    public function equals(Dependency $other) : bool;
+    public function equals(Dependency $other): bool;
 
-    public function toString() : string;
+    public function toString(): string;
 
-    public function __toString() : string;
+    public function __toString(): string;
 
-    public function namespaze() : Namespaze;
+    public function namespaze(): Namespaze;
 
-    public function isNamespaced() : bool;
+    public function isNamespaced(): bool;
 
-    public function inNamespaze(Namespaze $other) : bool;
+    public function inNamespaze(Namespaze $other): bool;
 }
diff --git a/src/Dependencies/DependencyFactory.php b/src/Dependencies/DependencyFactory.php
index f925ad6..56597f3 100644
--- a/src/Dependencies/DependencyFactory.php
+++ b/src/Dependencies/DependencyFactory.php
@@ -11,7 +11,7 @@ class DependencyFactory
      *
      * @return Dependency
      */
-    final public function createClazzFromStringArray(array $parts) : Dependency
+    final public function createClazzFromStringArray(array $parts): Dependency
     {
         try {
             $clazz = new Clazz(
@@ -29,7 +29,7 @@ final public function createClazzFromStringArray(array $parts) : Dependency
      *
      * @return AbstractClazz
      */
-    final public function createAbstractClazzFromStringArray(array $parts) : AbstractClazz
+    final public function createAbstractClazzFromStringArray(array $parts): AbstractClazz
     {
         return new AbstractClazz(
             $this->extractClazzPart($parts),
@@ -42,7 +42,7 @@ final public function createAbstractClazzFromStringArray(array $parts) : Abstrac
      *
      * @return Interfaze
      */
-    final public function createInterfazeFromStringArray(array $parts) : Interfaze
+    final public function createInterfazeFromStringArray(array $parts): Interfaze
     {
         return new Interfaze(
             $this->extractClazzPart($parts),
@@ -55,7 +55,7 @@ final public function createInterfazeFromStringArray(array $parts) : Interfaze
      *
      * @return Trait_
      */
-    final public function createTraitFromStringArray(array $parts) : Trait_
+    final public function createTraitFromStringArray(array $parts): Trait_
     {
         return new Trait_(
             $this->extractClazzPart($parts),
@@ -63,6 +63,19 @@ final public function createTraitFromStringArray(array $parts) : Trait_
         );
     }
 
+    /**
+     * @param array $parts
+     *
+     * @return Enum_
+     */
+    final public function createEnumFromStringArray(array $parts): Enum_
+    {
+        return new Enum_(
+            $this->extractClazzPart($parts),
+            new Namespaze($this->extractNamespaceParts($parts))
+        );
+    }
+
     /**
      * @param array $parts
      *
diff --git a/src/Dependencies/DependencyFilter.php b/src/Dependencies/DependencyFilter.php
index b9d2342..813c7d3 100644
--- a/src/Dependencies/DependencyFilter.php
+++ b/src/Dependencies/DependencyFilter.php
@@ -19,7 +19,7 @@ public function __construct(array $internals)
         $this->internals = $internals;
     }
 
-    public function filterByOptions(DependencyMap $dependencies, array $options) : DependencyMap
+    public function filterByOptions(DependencyMap $dependencies, array $options): DependencyMap
     {
         if (isset($options['underscore-namespaces']) && $options['underscore-namespaces'] === true) {
             $dependencies = $this->mapNamespaces($dependencies);
@@ -45,7 +45,7 @@ public function filterByOptions(DependencyMap $dependencies, array $options) : D
         return $dependencies;
     }
 
-    public function postFiltersByOptions(array $options) : \Closure
+    public function postFiltersByOptions(array $options): \Closure
     {
         $filters = [];
         if ($options['depth'] > 0) {
@@ -58,7 +58,7 @@ public function postFiltersByOptions(array $options) : \Closure
         return Functional::compose(...$filters);
     }
 
-    public function removeInternals(DependencyMap $dependencies) : DependencyMap
+    public function removeInternals(DependencyMap $dependencies): DependencyMap
     {
         return $dependencies->reduce(new DependencyMap(), function (DependencyMap $map, Dependency $from, Dependency $to) {
             return !in_array($to->toString(), $this->internals, true)
@@ -67,13 +67,13 @@ public function removeInternals(DependencyMap $dependencies) : DependencyMap
         });
     }
 
-    public function filterByNamespace(DependencyMap $dependencies, string $namespace) : DependencyMap
+    public function filterByNamespace(DependencyMap $dependencies, string $namespace): DependencyMap
     {
         $namespace = new Namespaze(array_filter(explode('\\', $namespace)));
         return $dependencies->reduce(new DependencyMap(), $this->filterNamespaceFn($namespace));
     }
 
-    public function excludeByRegex(DependencyMap $dependencies, string $regex) : DependencyMap
+    public function excludeByRegex(DependencyMap $dependencies, string $regex): DependencyMap
     {
         return $dependencies->reduce(new DependencyMap(), function (DependencyMap $map, Dependency $from, Dependency $to) use ($regex) {
             return preg_match($regex, $from->toString()) === 1 || preg_match($regex, $to->toString()) === 1
@@ -82,7 +82,7 @@ public function excludeByRegex(DependencyMap $dependencies, string $regex) : Dep
         });
     }
 
-    public function filterByFromNamespace(DependencyMap $dependencies, string $namespace) : DependencyMap
+    public function filterByFromNamespace(DependencyMap $dependencies, string $namespace): DependencyMap
     {
         $namespace = new Namespaze(array_filter(explode('\\', $namespace)));
         return $dependencies->reduce(new DependencyMap(), function (DependencyMap $map, Dependency $from, Dependency $to) use ($namespace) {
@@ -92,16 +92,16 @@ public function filterByFromNamespace(DependencyMap $dependencies, string $names
         });
     }
 
-    private function filterNamespaceFn(Namespaze $namespaze) : \Closure
+    private function filterNamespaceFn(Namespaze $namespaze): \Closure
     {
-        return function (DependencyMap $map, Dependency $from, Dependency $to) use ($namespaze) : DependencyMap {
+        return function (DependencyMap $map, Dependency $from, Dependency $to) use ($namespaze): DependencyMap {
             return $from->inNamespaze($namespaze) && $to->inNamespaze($namespaze)
                 ? $map->add($from, $to)
                 : $map;
         };
     }
 
-    public function filterByDepth(DependencyMap $dependencies, int $depth) : DependencyMap
+    public function filterByDepth(DependencyMap $dependencies, int $depth): DependencyMap
     {
         if ($depth === 0) {
             return clone $dependencies;
@@ -115,7 +115,7 @@ public function filterByDepth(DependencyMap $dependencies, int $depth) : Depende
         });
     }
 
-    public function filterClasses(DependencyMap $dependencies) : DependencyMap
+    public function filterClasses(DependencyMap $dependencies): DependencyMap
     {
         return $dependencies->reduce(new DependencyMap(), function (DependencyMap $map, Dependency $from, Dependency $to) {
             if ($from->namespaze()->count() === 0 || $to->namespaze()->count() === 0) {
@@ -125,21 +125,21 @@ public function filterClasses(DependencyMap $dependencies) : DependencyMap
         });
     }
 
-    public function reduceDependencyToNamespace() : \Closure
+    public function reduceDependencyToNamespace(): \Closure
     {
-        return function (Dependency $dependency) : Dependency {
+        return function (Dependency $dependency): Dependency {
             return $dependency->namespaze();
         };
     }
 
-    public function reduceDependencyByDepth(int $depth) : \Closure
+    public function reduceDependencyByDepth(int $depth): \Closure
     {
-        return function (Dependency $dependency) use ($depth) : Dependency {
+        return function (Dependency $dependency) use ($depth): Dependency {
             return $dependency->reduceToDepth($depth);
         };
     }
 
-    public function mapNamespaces(DependencyMap $dependencies) : DependencyMap
+    public function mapNamespaces(DependencyMap $dependencies): DependencyMap
     {
         return $dependencies->reduceEachDependency(function (Dependency $dependency) {
             if (strpos($dependency->toString(), '_') === false) {
diff --git a/src/Dependencies/DependencyMap.php b/src/Dependencies/DependencyMap.php
index f7070eb..45acaa6 100644
--- a/src/Dependencies/DependencyMap.php
+++ b/src/Dependencies/DependencyMap.php
@@ -14,7 +14,7 @@ class DependencyMap extends AbstractMap
      *
      * @return DependencyMap
      */
-    public function add(Dependency $from, Dependency $to) : self
+    public function add(Dependency $from, Dependency $to): self
     {
         $clone = clone $this;
         if ($from->equals($to)
@@ -35,14 +35,14 @@ public function add(Dependency $from, Dependency $to) : self
         return $clone;
     }
 
-    public function addMap(self $other) : self
+    public function addMap(self $other): self
     {
         return $this->reduce($other, function (DependencyMap $map, Dependency $from, Dependency $to) {
             return $map->add($from, $to);
         });
     }
 
-    public function addSet(Dependency $from, DependencySet $toSet) : self
+    public function addSet(Dependency $from, DependencySet $toSet): self
     {
         $clone = $toSet->reduce($this, function (DependencyMap $map, Dependency $to) use ($from) {
             return $map->add($from, $to);
@@ -50,19 +50,19 @@ public function addSet(Dependency $from, DependencySet $toSet) : self
         return $clone;
     }
 
-    public function get(Dependency $from) : DependencySet
+    public function get(Dependency $from): DependencySet
     {
         return $this->map[$from->toString()][self::$VALUE];
     }
 
-    public function fromDependencies() : DependencySet
+    public function fromDependencies(): DependencySet
     {
         return $this->reduce(new DependencySet(), function (DependencySet $set, Dependency $from) {
             return $set->add($from);
         });
     }
 
-    public function allDependencies() : DependencySet
+    public function allDependencies(): DependencySet
     {
         return $this->reduce(new DependencySet(), function (DependencySet $set, Dependency $from, Dependency $to) {
             return $set
@@ -71,7 +71,7 @@ public function allDependencies() : DependencySet
         });
     }
 
-    public function mapAllDependencies(\Closure $mappers) : DependencySet
+    public function mapAllDependencies(\Closure $mappers): DependencySet
     {
         return $this->reduce(new DependencySet(), function (DependencySet $set, Dependency $from, Dependency $to) use ($mappers) {
             return $set
@@ -88,14 +88,14 @@ public function mapAllDependencies(\Closure $mappers) : DependencySet
      *
      * @return DependencyMap
      */
-    public function reduceEachDependency(\Closure $mappers) : DependencyMap
+    public function reduceEachDependency(\Closure $mappers): DependencyMap
     {
         return $this->reduce(new self(), function (self $map, Dependency $from, Dependency $to) use ($mappers) {
             return $map->add($mappers($from), $mappers($to));
         });
     }
 
-    public function toString() : string
+    public function toString(): string
     {
         return trim($this->reduce('', function (string $carry, Dependency $key, Dependency $value) {
             return $carry.$key->toString().' --> '.$value->toString().PHP_EOL;
diff --git a/src/Dependencies/DependencySet.php b/src/Dependencies/DependencySet.php
index 53de71c..c706a5c 100644
--- a/src/Dependencies/DependencySet.php
+++ b/src/Dependencies/DependencySet.php
@@ -13,7 +13,7 @@ class DependencySet extends AbstractCollection
      *
      * @return DependencySet
      */
-    public function add(Dependency $dependency) : DependencySet
+    public function add(Dependency $dependency): DependencySet
     {
         $clone = clone $this;
         if ($this->contains($dependency)
diff --git a/src/Dependencies/Enum_.php b/src/Dependencies/Enum_.php
new file mode 100644
index 0000000..f29a8f6
--- /dev/null
+++ b/src/Dependencies/Enum_.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mihaeu\PhpDependencies\Dependencies;
+
+class Enum_ extends ClazzLike
+{
+}
diff --git a/src/Dependencies/Namespaze.php b/src/Dependencies/Namespaze.php
index 0ce083a..aa98c66 100644
--- a/src/Dependencies/Namespaze.php
+++ b/src/Dependencies/Namespaze.php
@@ -32,12 +32,12 @@ private function ensureNamespaceIsValid(array $parts)
         }
     }
 
-    public function count() : int
+    public function count(): int
     {
         return count($this->parts);
     }
 
-    public function namespaze() : Namespaze
+    public function namespaze(): Namespaze
     {
         return $this;
     }
@@ -45,12 +45,12 @@ public function namespaze() : Namespaze
     /**
      * @return string[]
      */
-    public function parts() : array
+    public function parts(): array
     {
         return $this->parts;
     }
 
-    public function reduceToDepth(int $maxDepth) : Dependency
+    public function reduceToDepth(int $maxDepth): Dependency
     {
         if ($maxDepth === 0 || $this->count() === $maxDepth) {
             return $this;
@@ -61,29 +61,29 @@ public function reduceToDepth(int $maxDepth) : Dependency
             : new self(array_slice($this->parts, 0, $maxDepth));
     }
 
-    public function reduceDepthFromLeftBy(int $reduction) : Dependency
+    public function reduceDepthFromLeftBy(int $reduction): Dependency
     {
         return $reduction >= $this->count()
             ? new self([])
             : new self(array_slice($this->parts, $reduction));
     }
 
-    public function equals(Dependency $other) : bool
+    public function equals(Dependency $other): bool
     {
         return $this->toString() === $other->toString();
     }
 
-    public function toString() : string
+    public function toString(): string
     {
         return implode('\\', $this->parts);
     }
 
-    public function __toString() : string
+    public function __toString(): string
     {
         return $this->toString();
     }
 
-    public function inNamespaze(Namespaze $other) : bool
+    public function inNamespaze(Namespaze $other): bool
     {
         return $other->toString() !== ''
             && $this->toString() !== ''
@@ -95,7 +95,7 @@ public function inNamespaze(Namespaze $other) : bool
      *
      * @return bool
      */
-    private function arrayContainsNotOnlyStrings(array $parts):bool
+    private function arrayContainsNotOnlyStrings(array $parts): bool
     {
         return Util::array_once($parts, function ($value) {
             return !is_string($value);
diff --git a/src/Dependencies/NullDependency.php b/src/Dependencies/NullDependency.php
index cb27d5e..8323574 100644
--- a/src/Dependencies/NullDependency.php
+++ b/src/Dependencies/NullDependency.php
@@ -6,22 +6,22 @@
 
 class NullDependency implements Dependency
 {
-    public function reduceToDepth(int $maxDepth) : Dependency
+    public function reduceToDepth(int $maxDepth): Dependency
     {
         return new NullDependency();
     }
 
-    public function reduceDepthFromLeftBy(int $reduction) : Dependency
+    public function reduceDepthFromLeftBy(int $reduction): Dependency
     {
         return new NullDependency();
     }
 
-    public function equals(Dependency $other) : bool
+    public function equals(Dependency $other): bool
     {
         return false;
     }
 
-    public function toString() : string
+    public function toString(): string
     {
         return '';
     }
@@ -29,22 +29,22 @@ public function toString() : string
     /**
      * @return string
      */
-    public function __toString() : string
+    public function __toString(): string
     {
         return $this->toString();
     }
 
-    public function namespaze() : Namespaze
+    public function namespaze(): Namespaze
     {
         return new Namespaze([]);
     }
 
-    public function inNamespaze(Namespaze $other) : bool
+    public function inNamespaze(Namespaze $other): bool
     {
         return false;
     }
 
-    public function count()
+    public function count(): int
     {
         return 0;
     }
diff --git a/src/Exceptions/ParserException.php b/src/Exceptions/ParserException.php
index ba1255c..ab5dcbf 100644
--- a/src/Exceptions/ParserException.php
+++ b/src/Exceptions/ParserException.php
@@ -9,4 +9,4 @@ public function __construct(string $message, string $file)
         $this->message = $message;
         $this->file = $file;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Formatters/DependencyStructureMatrixBuilder.php b/src/Formatters/DependencyStructureMatrixBuilder.php
index a4225b9..3eb7a0b 100644
--- a/src/Formatters/DependencyStructureMatrixBuilder.php
+++ b/src/Formatters/DependencyStructureMatrixBuilder.php
@@ -10,10 +10,10 @@
 
 class DependencyStructureMatrixBuilder
 {
-    public function buildMatrix(DependencyMap $dependencies, \Closure $mappers) : array
+    public function buildMatrix(DependencyMap $dependencies, \Closure $mappers): array
     {
         $emptyDsm = $this->createEmptyDsm($dependencies->mapAllDependencies($mappers));
-        return $dependencies->reduce($emptyDsm, function (array $dsm, Dependency $from, Dependency $to) use ($mappers) : array {
+        return $dependencies->reduce($emptyDsm, function (array $dsm, Dependency $from, Dependency $to) use ($mappers): array {
             $from = $mappers($from)->toString();
             $to = $mappers($to)->toString();
             $dsm[$to][$from] += 1;
diff --git a/src/Formatters/DependencyStructureMatrixHtmlFormatter.php b/src/Formatters/DependencyStructureMatrixHtmlFormatter.php
index 0f37afa..3ab413c 100644
--- a/src/Formatters/DependencyStructureMatrixHtmlFormatter.php
+++ b/src/Formatters/DependencyStructureMatrixHtmlFormatter.php
@@ -23,7 +23,7 @@ public function __construct(DependencyStructureMatrixBuilder $dependencyStructur
     /**
      * {@inheritdoc}
      */
-    public function format(DependencyMap $all, \Closure $mappers = null) : string
+    public function format(DependencyMap $all, \Closure $mappers = null): string
     {
         return $this->buildHtmlTable(
             $this->dependencyStructureMatrixBuilder->buildMatrix($all, $mappers ?? Functional::id())
@@ -35,7 +35,7 @@ public function format(DependencyMap $all, \Closure $mappers = null) : string
      *
      * @return string
      */
-    private function buildHtmlTable(array $dependencyArray) : string
+    private function buildHtmlTable(array $dependencyArray): string
     {
         return '<table>'
             .$this->tableHead($dependencyArray)
diff --git a/src/Formatters/DotFormatter.php b/src/Formatters/DotFormatter.php
index c8ab960..e830256 100644
--- a/src/Formatters/DotFormatter.php
+++ b/src/Formatters/DotFormatter.php
@@ -10,7 +10,7 @@
 
 class DotFormatter implements Formatter
 {
-    public function format(DependencyMap $map, \Closure $mappers = null) : string
+    public function format(DependencyMap $map, \Closure $mappers = null): string
     {
         return 'digraph generated_by_dePHPend {'.PHP_EOL
             .$map->reduceEachDependency($mappers ?? Functional::id())->reduce('', function (string $carry, Dependency $from, Dependency $to) {
diff --git a/src/Formatters/Formatter.php b/src/Formatters/Formatter.php
index 94a78f1..187a7fe 100644
--- a/src/Formatters/Formatter.php
+++ b/src/Formatters/Formatter.php
@@ -13,5 +13,5 @@ interface Formatter
      *
      * @return string
      */
-    public function format(DependencyMap $map, \Closure $mappers = null) : string;
+    public function format(DependencyMap $map, \Closure $mappers = null): string;
 }
diff --git a/src/Formatters/PlantUmlFormatter.php b/src/Formatters/PlantUmlFormatter.php
index cece6c6..98b2417 100644
--- a/src/Formatters/PlantUmlFormatter.php
+++ b/src/Formatters/PlantUmlFormatter.php
@@ -15,7 +15,7 @@ class PlantUmlFormatter implements Formatter
     /**
      * {@inheritdoc}
      */
-    public function format(DependencyMap $map, \Closure $mappers = null) : string
+    public function format(DependencyMap $map, \Closure $mappers = null): string
     {
         return '@startuml'.PHP_EOL
             .$this->plantUmlNamespaceDefinitions($map).PHP_EOL
@@ -23,7 +23,7 @@ public function format(DependencyMap $map, \Closure $mappers = null) : string
             .'@enduml';
     }
 
-    private function dependenciesInPlantUmlFormat(DependencyMap $map) : string
+    private function dependenciesInPlantUmlFormat(DependencyMap $map): string
     {
         return str_replace(
             ['-->', '\\'],
@@ -32,7 +32,7 @@ private function dependenciesInPlantUmlFormat(DependencyMap $map) : string
         );
     }
 
-    private function plantUmlNamespaceDefinitions(DependencyMap $map) : string
+    private function plantUmlNamespaceDefinitions(DependencyMap $map): string
     {
         $namespaces = $map->reduce(new DependencySet(), function (DependencySet $set, Dependency $from, Dependency $to) {
             return $set
@@ -44,7 +44,7 @@ private function plantUmlNamespaceDefinitions(DependencyMap $map) : string
         );
     }
 
-    private function buildNamespaceTree(DependencySet $namespaces) : array
+    private function buildNamespaceTree(DependencySet $namespaces): array
     {
         return $namespaces->reduce([], function (array $total, Namespaze $namespaze) {
             $currentLevel = &$total;
@@ -58,9 +58,9 @@ private function buildNamespaceTree(DependencySet $namespaces) : array
         });
     }
 
-    private function printNamespaceTree(array $buildNamespaceTree) : string
+    private function printNamespaceTree(array $buildNamespaceTree): string
     {
-        return Util::reduce($buildNamespaceTree, function (string $total, string $namespace, array $children) : string {
+        return Util::reduce($buildNamespaceTree, function (string $total, string $namespace, array $children): string {
             return  $total.'namespace '.$namespace.' {'.PHP_EOL.$this->printNamespaceTree($children).'}'.PHP_EOL;
         }, '');
     }
diff --git a/src/OS/PhpFile.php b/src/OS/PhpFile.php
index 1937138..f2a6f8e 100644
--- a/src/OS/PhpFile.php
+++ b/src/OS/PhpFile.php
@@ -19,7 +19,7 @@ public function __construct(\SplFileInfo $file)
         $this->file = $file;
     }
 
-    public function file() : \SplFileInfo
+    public function file(): \SplFileInfo
     {
         return $this->file;
     }
@@ -34,7 +34,7 @@ public function code()
         return @file_get_contents($this->file->getPathname());
     }
 
-    public function toString() : string
+    public function toString(): string
     {
         return (string) $this->file;
     }
@@ -42,7 +42,7 @@ public function toString() : string
     /**
      * @return string
      */
-    public function __toString() : string
+    public function __toString(): string
     {
         return $this->toString();
     }
diff --git a/src/OS/PhpFileFinder.php b/src/OS/PhpFileFinder.php
index 91e4f51..5648023 100644
--- a/src/OS/PhpFileFinder.php
+++ b/src/OS/PhpFileFinder.php
@@ -6,14 +6,14 @@
 
 class PhpFileFinder
 {
-    public function find(\SplFileInfo $file) : PhpFileSet
+    public function find(\SplFileInfo $file): PhpFileSet
     {
         return $file->isDir()
             ? $this->findInDir($file)
             : (new PhpFileSet())->add(new PhpFile($file));
     }
 
-    private function findInDir(\SplFileInfo $dir) : PhpFileSet
+    private function findInDir(\SplFileInfo $dir): PhpFileSet
     {
         $collection = new PhpFileSet();
         $regexIterator = new \RegexIterator(
@@ -35,7 +35,7 @@ private function findInDir(\SplFileInfo $dir) : PhpFileSet
      *
      * @return PhpFileSet
      */
-    public function getAllPhpFilesFromSources(array $sources) : PhpFileSet
+    public function getAllPhpFilesFromSources(array $sources): PhpFileSet
     {
         return array_reduce(
             $sources,
diff --git a/src/OS/PhpFileSet.php b/src/OS/PhpFileSet.php
index 655804f..f872550 100644
--- a/src/OS/PhpFileSet.php
+++ b/src/OS/PhpFileSet.php
@@ -8,7 +8,7 @@
 
 class PhpFileSet extends AbstractCollection
 {
-    public function add(PhpFile $file) : PhpFileSet
+    public function add(PhpFile $file): PhpFileSet
     {
         $clone = clone $this;
         if ($this->contains($file)) {
@@ -19,14 +19,14 @@ public function add(PhpFile $file) : PhpFileSet
         return $clone;
     }
 
-    public function addAll(PhpFileSet $otherCollection) : PhpFileSet
+    public function addAll(PhpFileSet $otherCollection): PhpFileSet
     {
         return $otherCollection->reduce(clone $this, function (self $set, PhpFile $file) {
             return $set->add($file);
         });
     }
 
-    public function contains($other) : bool
+    public function contains($other): bool
     {
         return $this->any(function (PhpFile $file) use ($other) {
             return $file->equals($other);
diff --git a/src/OS/ShellWrapper.php b/src/OS/ShellWrapper.php
index d28fc1b..6f70b82 100644
--- a/src/OS/ShellWrapper.php
+++ b/src/OS/ShellWrapper.php
@@ -15,7 +15,7 @@ class ShellWrapper
      *
      * @return int return var
      */
-    public function run(string $command) : int
+    public function run(string $command): int
     {
         $output = [];
         $returnVar = 1;
diff --git a/src/Util/AbstractCollection.php b/src/Util/AbstractCollection.php
index dfbc64e..3776a85 100644
--- a/src/Util/AbstractCollection.php
+++ b/src/Util/AbstractCollection.php
@@ -12,7 +12,7 @@ abstract class AbstractCollection implements Collection
     /**
      * {@inheritdoc}
      */
-    public function any(\Closure $closure) : bool
+    public function any(\Closure $closure): bool
     {
         foreach ($this->collection as $item) {
             if ($closure($item) === true) {
@@ -28,7 +28,7 @@ public function any(\Closure $closure) : bool
      *
      * @return bool
      */
-    public function none(\Closure $closure) : bool
+    public function none(\Closure $closure): bool
     {
         return !$this->any($closure);
     }
@@ -46,7 +46,7 @@ public function each(\Closure $closure)
     /**
      * {@inheritdoc}
      */
-    public function mapToArray(\Closure $closure) : array
+    public function mapToArray(\Closure $closure): array
     {
         return array_map($closure, $this->collection);
     }
@@ -62,7 +62,7 @@ public function reduce($initial, \Closure $closure)
     /**
      * {@inheritdoc}
      */
-    public function filter(\Closure $closure) : Collection
+    public function filter(\Closure $closure): Collection
     {
         $clone = clone $this;
         $clone->collection = array_values(array_filter($this->collection, $closure));
@@ -73,7 +73,7 @@ public function filter(\Closure $closure) : Collection
     /**
      * {@inheritdoc}
      */
-    public function toArray() : array
+    public function toArray(): array
     {
         return $this->collection;
     }
@@ -81,7 +81,7 @@ public function toArray() : array
     /**
      * {@inheritdoc}
      */
-    public function count()
+    public function count(): int
     {
         return count($this->collection);
     }
@@ -89,12 +89,12 @@ public function count()
     /**
      * {@inheritdoc}
      */
-    public function contains($other) : bool
+    public function contains($other): bool
     {
         return in_array($other, $this->collection);
     }
 
-    public function toString() : string
+    public function toString(): string
     {
         return implode(PHP_EOL, $this->mapToArray(function ($x) {
             return $x->toString();
@@ -104,12 +104,12 @@ public function toString() : string
     /**
      * @return string
      */
-    public function __toString() : string
+    public function __toString(): string
     {
         return $this->toString();
     }
 
-    public function equals(Collection $other) : bool
+    public function equals(Collection $other): bool
     {
         return $this->toString() === $other->toString();
     }
diff --git a/src/Util/AbstractMap.php b/src/Util/AbstractMap.php
index 6f5e089..ec2050e 100644
--- a/src/Util/AbstractMap.php
+++ b/src/Util/AbstractMap.php
@@ -15,7 +15,7 @@ abstract class AbstractMap implements Collection
     /**
      * @inheritDoc
      */
-    public function any(\Closure $closure) : bool
+    public function any(\Closure $closure): bool
     {
         foreach ($this->map as $item) {
             foreach ($item[self::$VALUE]->toArray() as $subItem) {
@@ -30,7 +30,7 @@ public function any(\Closure $closure) : bool
     /**
      * @inheritDoc
      */
-    public function none(\Closure $closure) : bool
+    public function none(\Closure $closure): bool
     {
         return !$this->any($closure);
     }
@@ -50,7 +50,7 @@ public function each(\Closure $closure)
     /**
      * @inheritDoc
      */
-    public function mapToArray(\Closure $closure) : array
+    public function mapToArray(\Closure $closure): array
     {
         $xs = [];
         foreach ($this->map as $item) {
@@ -77,7 +77,7 @@ public function reduce($initial, \Closure $closure)
     /**
      * @inheritDoc
      */
-    public function filter(\Closure $closure) : Collection
+    public function filter(\Closure $closure): Collection
     {
         $clone = clone $this;
         $clone->map = [];
@@ -94,7 +94,7 @@ public function filter(\Closure $closure) : Collection
     /**
      * @inheritDoc
      */
-    public function toArray() : array
+    public function toArray(): array
     {
         return $this->map;
     }
@@ -102,7 +102,7 @@ public function toArray() : array
     /**
      * @inheritDoc
      */
-    public function contains($other) : bool
+    public function contains($other): bool
     {
         foreach ($this->map as $key => $item) {
             if ($item[self::$KEY] instanceof $other && $item[self::$KEY]->equals($other)) {
@@ -115,12 +115,12 @@ public function contains($other) : bool
     /**
      * @inheritDoc
      */
-    abstract public function toString() : string;
+    abstract public function toString(): string;
 
     /**
      * @inheritDoc
      */
-    public function equals(Collection $other) : bool
+    public function equals(Collection $other): bool
     {
         return $this instanceof $other
             && $this->toString() === $other->toString();
@@ -129,7 +129,7 @@ public function equals(Collection $other) : bool
     /**
      * @inheritDoc
      */
-    public function count()
+    public function count(): int
     {
         return count($this->map);
     }
diff --git a/src/Util/Collection.php b/src/Util/Collection.php
index 9ad7a6f..c4dd6f1 100644
--- a/src/Util/Collection.php
+++ b/src/Util/Collection.php
@@ -13,14 +13,14 @@ interface Collection extends \Countable
      *
      * @return bool
      */
-    public function any(\Closure $closure) : bool;
+    public function any(\Closure $closure): bool;
 
     /**
      * @param \Closure $closure
      *
      * @return bool
      */
-    public function none(\Closure $closure) : bool;
+    public function none(\Closure $closure): bool;
 
     /**
      * Applies $closure to each element.
@@ -36,7 +36,7 @@ public function each(\Closure $closure);
      *
      * @return array
      */
-    public function mapToArray(\Closure $closure) : array;
+    public function mapToArray(\Closure $closure): array;
 
     /**
      * @param mixed    $initial
@@ -51,29 +51,29 @@ public function reduce($initial, \Closure $closure);
      *
      * @return Collection
      */
-    public function filter(\Closure $closure) : Collection;
+    public function filter(\Closure $closure): Collection;
 
     /**
      * @return array
      */
-    public function toArray() : array;
+    public function toArray(): array;
 
     /**
      * @param $other
      *
      * @return bool
      */
-    public function contains($other) : bool;
+    public function contains($other): bool;
 
     /**
      * @return string
      */
-    public function toString() : string;
+    public function toString(): string;
 
     /**
      * @param Collection $other
      *
      * @return bool
      */
-    public function equals(Collection $other) : bool;
+    public function equals(Collection $other): bool;
 }
diff --git a/src/Util/Functional.php b/src/Util/Functional.php
index 7093d9d..e652d6b 100644
--- a/src/Util/Functional.php
+++ b/src/Util/Functional.php
@@ -13,7 +13,7 @@ public static function id()
         };
     }
 
-    public static function compose(...$functions) : \Closure
+    public static function compose(...$functions): \Closure
     {
         return array_reduce(
             $functions,
diff --git a/src/Util/Util.php b/src/Util/Util.php
index 7eb4e2c..ee9275e 100644
--- a/src/Util/Util.php
+++ b/src/Util/Util.php
@@ -15,7 +15,7 @@ class Util
      *
      * @return bool
      */
-    public static function array_once(array $xs, \Closure $fn) : bool
+    public static function array_once(array $xs, \Closure $fn): bool
     {
         foreach ($xs as $index => $value) {
             if ($fn($value, $index)) {
diff --git a/tests/feature/DsmTest.php b/tests/feature/DsmTest.php
index 20fcb19..94a6aba 100644
--- a/tests/feature/DsmTest.php
+++ b/tests/feature/DsmTest.php
@@ -10,7 +10,7 @@ class DsmTest extends TestCase
 {
     public function testCreatesSimpleDsmInHtml(): void
     {
-        assertRegExp(
+        $this->assertMatchesRegularExpression(
             '@\d: PhpParser</th><td>([1-9]\d*).+.+@s',
             shell_exec(DEPHPEND_BIN.' dsm '.SRC_PATH.' --no-classes --depth=2 --format=html')
         );
diff --git a/tests/feature/HelpTest.php b/tests/feature/HelpTest.php
index 77cda37..4b50bf6 100644
--- a/tests/feature/HelpTest.php
+++ b/tests/feature/HelpTest.php
@@ -10,16 +10,16 @@ class HelpTest extends TestCase
 {
     public function testNoArgumentsShowsHelp(): void
     {
-        self::assertRegExp('/command \[options\] \[arguments\].*/s', shell_exec(DEPHPEND_BIN));
+        $this->assertMatchesRegularExpression('/command \[options\] \[arguments\].*/s', shell_exec(DEPHPEND_BIN));
     }
 
     public function testHelpShowsHelp(): void
     {
-        self::assertRegExp('/Usage:.*Options:.*Help:.*/s', shell_exec(DEPHPEND_BIN.' help'));
+        $this->assertMatchesRegularExpression('/Usage:.*Options:.*Help:.*/s', shell_exec(DEPHPEND_BIN.' help'));
     }
 
     public function testShowsHelpForCommand(): void
     {
-        self::assertRegExp('/Arguments:.*source.*Options:.*--internals.*/s', shell_exec(DEPHPEND_BIN.' help text'));
+        $this->assertMatchesRegularExpression('/Arguments:.*source.*Options:.*--internals.*/s', shell_exec(DEPHPEND_BIN.' help text'));
     }
 }
diff --git a/tests/feature/ListTest.php b/tests/feature/ListTest.php
index a441fcf..94dd0f5 100644
--- a/tests/feature/ListTest.php
+++ b/tests/feature/ListTest.php
@@ -10,6 +10,6 @@ class ListTest extends TestCase
 {
     public function testNoArgumentsShowsHelp(): void
     {
-        assertRegExp('/dsm.*metrics.*text.*uml.*/s', shell_exec(DEPHPEND_BIN.' list'));
+        $this->assertMatchesRegularExpression('/dsm.*metrics.*text.*uml.*/s', shell_exec(DEPHPEND_BIN.' list'));
     }
 }
diff --git a/tests/feature/MetricsTest.php b/tests/feature/MetricsTest.php
index c6e84f4..8bacf17 100644
--- a/tests/feature/MetricsTest.php
+++ b/tests/feature/MetricsTest.php
@@ -10,7 +10,7 @@ class MetricsTest extends TestCase
 {
     public function testComputeMetricsForDephpend(): void
     {
-        assertRegExp(
+        $this->assertMatchesRegularExpression(
             '/Classes:.*\d\d.*Abstract classes:.*\d+.*Abstractness:.*\d\.\d+/s',
             shell_exec(DEPHPEND_BIN.' metrics '.SRC_PATH)
         );
diff --git a/tests/feature/TextTest.php b/tests/feature/TextTest.php
index cc8dbd8..b6c57bd 100644
--- a/tests/feature/TextTest.php
+++ b/tests/feature/TextTest.php
@@ -8,10 +8,9 @@
 
 class TextTest extends TestCase
 {
-
     public function testTextCommandOnDephpendSourceWithoutClassesAndWithRegexAndFromFilter(): void
     {
-        assertEquals(
+        $this->assertEquals(
             'Mihaeu\PhpDependencies\Analyser --> Mihaeu\PhpDependencies\Dependencies'.PHP_EOL
             .'Mihaeu\PhpDependencies\Analyser --> Mihaeu\PhpDependencies\OS'.PHP_EOL,
             shell_exec(DEPHPEND_BIN.' text '.SRC_PATH
diff --git a/tests/feature/UmlTest.php b/tests/feature/UmlTest.php
index 9a22316..d850b82 100644
--- a/tests/feature/UmlTest.php
+++ b/tests/feature/UmlTest.php
@@ -44,7 +44,7 @@ public function testCreatesUml(): void
         $tempFileUml = sys_get_temp_dir().'/dephpend-uml-test.uml';
         shell_exec(DEPHPEND_BIN.' uml '.SRC_PATH.' --no-classes --keep-uml '
             .'--output="'.$tempFilePng.'" -f Mihaeu\\\\PhpDependencies\\\\OS');
-        assertEquals(
+        $this->assertEquals(
             $expected,
             file_get_contents($tempFileUml)
         );
diff --git a/tests/samples/CreatingObjectsFeature.php b/tests/samples/CreatingObjectsFeature.php
index 84155d0..eb8c548 100644
--- a/tests/samples/CreatingObjectsFeature.php
+++ b/tests/samples/CreatingObjectsFeature.php
@@ -7,6 +7,6 @@ class A
     public function test(): void
     {
         new B();
-        new C;
+        new C();
     }
 }
diff --git a/tests/samples/KnownVariablePassedIntoMethodWithoutTypeHintsFeature.php b/tests/samples/KnownVariablePassedIntoMethodWithoutTypeHintsFeature.php
index 9915c50..2b5fa43 100644
--- a/tests/samples/KnownVariablePassedIntoMethodWithoutTypeHintsFeature.php
+++ b/tests/samples/KnownVariablePassedIntoMethodWithoutTypeHintsFeature.php
@@ -7,7 +7,7 @@ class A
 {
     public function test(): void
     {
-        $b = new B;
+        $b = new B();
         new C($b);
     }
 }
diff --git a/tests/samples/ParamReturnThrowsInDocCommentFeature.php b/tests/samples/ParamReturnThrowsInDocCommentFeature.php
index 6e720a3..68bac63 100644
--- a/tests/samples/ParamReturnThrowsInDocCommentFeature.php
+++ b/tests/samples/ParamReturnThrowsInDocCommentFeature.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 $test = '
 class A {
diff --git a/tests/samples/Php7ReturnValueDeclarationFeature.php b/tests/samples/Php7ReturnValueDeclarationFeature.php
index 65c10ad..e0f6a98 100644
--- a/tests/samples/Php7ReturnValueDeclarationFeature.php
+++ b/tests/samples/Php7ReturnValueDeclarationFeature.php
@@ -3,7 +3,7 @@
 
 class A
 {
-    public function test() : B
+    public function test(): B
     {
         return null;
     }
diff --git a/tests/samples/ReturnValueOfKnownMethodFeature.php b/tests/samples/ReturnValueOfKnownMethodFeature.php
index b546209..8aa9a07 100644
--- a/tests/samples/ReturnValueOfKnownMethodFeature.php
+++ b/tests/samples/ReturnValueOfKnownMethodFeature.php
@@ -13,7 +13,7 @@ public function test(): void
 
 class B
 {
-    public function x() : C
+    public function x(): C
     {
         return new C();
     }
diff --git a/tests/samples/UsingEnumsFeature.php b/tests/samples/UsingEnumsFeature.php
new file mode 100644
index 0000000..05c772a
--- /dev/null
+++ b/tests/samples/UsingEnumsFeature.php
@@ -0,0 +1,16 @@
+# B --> A
+<?php
+
+enum A: string
+{
+    case Foo = 'foo';
+    case Bar = 'bar';
+}
+
+class B
+{
+    public function x(): A
+    {
+        return A::Foo;
+    }
+}
diff --git a/tests/samples/UsingTraitsFeature.php b/tests/samples/UsingTraitsFeature.php
index 32a0208..3fbe91c 100644
--- a/tests/samples/UsingTraitsFeature.php
+++ b/tests/samples/UsingTraitsFeature.php
@@ -6,5 +6,6 @@
 class A
 {
     use B;
-    use C, D;
+    use C;
+    use D;
 }
diff --git a/tests/unit/Analyser/DefaultParserTest.php b/tests/unit/Analyser/DefaultParserTest.php
index ac885a5..09aa28a 100644
--- a/tests/unit/Analyser/DefaultParserTest.php
+++ b/tests/unit/Analyser/DefaultParserTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Mihaeu\PhpDependencies\Analyser;
 
@@ -15,6 +17,6 @@ public function testPassesCodeToBaseParser(): void
         $baseParser = $this->createMock(Parser::class);
         $baseParser->method('parse')->willReturn(['test']);
         $parser = new DefaultParser($baseParser);
-        assertEquals(['test'], $parser->parse(''));
+        $this->assertEquals(['test'], $parser->parse(''));
     }
 }
diff --git a/tests/unit/Analyser/DependencyInspectionVisitorTest.php b/tests/unit/Analyser/DependencyInspectionVisitorTest.php
index 99611ae..5ebc2cf 100644
--- a/tests/unit/Analyser/DependencyInspectionVisitorTest.php
+++ b/tests/unit/Analyser/DependencyInspectionVisitorTest.php
@@ -77,7 +77,7 @@ protected function setUp(): void
      *
      * @return bool
      */
-    private function dependenciesContain(DependencyMap $dependencies, Dependency $otherDependency) : bool
+    private function dependenciesContain(DependencyMap $dependencies, Dependency $otherDependency): bool
     {
         return $dependencies->any(function (Dependency $from, Dependency $to) use ($otherDependency) {
             return $from->equals($otherDependency)
@@ -122,7 +122,7 @@ public function testDetectsExplicitNewCreation(): void
         $this->dependencyInspectionVisitor->enterNode($newNode);
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain($this->dependencyInspectionVisitor->dependencies(), new Clazz('TestDep')));
+        $this->assertTrue($this->dependenciesContain($this->dependencyInspectionVisitor->dependencies(), new Clazz('TestDep')));
     }
 
     public function testDetectsExtendedClasses(): void
@@ -136,7 +136,7 @@ public function testDetectsExtendedClasses(): void
         $this->dependencyInspectionVisitor->enterNode($node);
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('ClassA', new Namespaze(['A', 'a', '1']))
         ));
@@ -157,11 +157,11 @@ public function testDetectsWhenInterfacesImplementMultipleInterfaces(): void
         $this->dependencyInspectionVisitor->enterNode($node);
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('ClassA', new Namespaze(['A', 'a', '1']))
         ));
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('ClassB', new Namespaze(['B', 'b', '2']))
         ));
@@ -177,7 +177,7 @@ public function testDetectsAbstractClasses(): void
         $this->addRandomDependency();
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new AbstractClazz('Test', new Namespaze(['A']))
         ));
@@ -193,7 +193,7 @@ public function testDetectsInterfaces(): void
         $this->addRandomDependency();
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Interfaze('Test', new Namespaze(['A']))
         ));
@@ -213,11 +213,11 @@ public function testDetectsImplementedInterfaces(): void
         $this->dependencyInspectionVisitor->enterNode($node);
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('InterfaceOne', new Namespaze(['A', 'B']))
         ));
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('InterfaceTwo', new Namespaze(['C', 'D']))
         ));
@@ -229,7 +229,7 @@ public function testIgnoresInnerClassesWithoutName(): void
         $this->dependencyInspectionVisitor->enterNode($node);
         $this->dependencyInspectionVisitor->leaveNode($node);
 
-        assertEmpty($this->dependencyInspectionVisitor->dependencies());
+        $this->assertEmpty($this->dependencyInspectionVisitor->dependencies());
     }
 
     public function testDetectsDependenciesFromMethodArguments(): void
@@ -248,11 +248,11 @@ public function testDetectsDependenciesFromMethodArguments(): void
 
         $this->addNodeToAst($methodNode);
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('DependencyOne', new Namespaze(['A', 'B']))
         ));
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('DependencyTwo', new Namespaze(['A', 'B']))
         ));
@@ -266,7 +266,7 @@ public function testDetectsUseNodes(): void
             )
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('Test', new Namespaze(['A', 'a', '1']))
         ));
@@ -278,7 +278,7 @@ public function testReturnType(): void
             new ClassMethod('', ['returnType' => new Name(['Namespace', 'Test'])])
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('Test', new Namespaze(['Namespace']))
         ));
@@ -293,7 +293,7 @@ public function testDetectsCallsOnStaticClasses(): void
         $this->dependencyInspectionVisitor->enterNode($staticCall);
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('Singleton', new Namespaze(['A', 'a', '1']))
         ));
@@ -307,7 +307,7 @@ public function testAddsDependenciesOnlyWhenInClassContext(): void
         // we leave the ClassNode, but we haven't entered it, so class context is unknown
         $this->dependencyInspectionVisitor->leaveNode(new ClassNode('test'));
         $dependencies = $this->dependencyInspectionVisitor->dependencies();
-        assertEmpty($dependencies);
+        $this->assertEmpty($dependencies);
     }
 
     public function testTrait(): void
@@ -320,7 +320,7 @@ public function testTrait(): void
         $this->addRandomDependency();
 
         $this->dependencyInspectionVisitor->leaveNode($node);
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Trait_('Test', new Namespaze(['A']))
         ));
@@ -332,7 +332,7 @@ public function testUseSingleTrait(): void
             new TraitUse([new Name(['A', 'Test'])])
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Trait_('Test', new Namespaze(['A']))
         ));
@@ -348,15 +348,15 @@ public function testUseMultipleTraits(): void
             ])
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Trait_('Test', new Namespaze(['A']))
         ));
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Trait_('Test2', new Namespaze(['B']))
         ));
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Trait_('Test3', new Namespaze(['C']))
         ));
@@ -368,7 +368,7 @@ public function testUseInstanceofComparison(): void
             new Instanceof_(new Array_(), new FullyQualifiedNameNode('Test'))
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('Test')
         ));
@@ -380,7 +380,7 @@ public function testDetectsCatchNode(): void
             new Catch_([new Name(['AnException'])], new Variable('e'))
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('AnException')
         ));
@@ -395,11 +395,11 @@ public function testDetectsPhp71MultipleCatchNodes(): void
             ], new Variable('e'))
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('AnException')
         ));
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('AnotherException')
         ));
@@ -411,7 +411,7 @@ public function testDetectsFetchClassNode(): void
             new ClassConstFetch(new Name('StaticTest'), 'test')
         );
 
-        assertTrue($this->dependenciesContain(
+        $this->assertTrue($this->dependenciesContain(
             $this->dependencyInspectionVisitor->dependencies(),
             new Clazz('StaticTest')
         ));
diff --git a/tests/unit/Analyser/MetricsTest.php b/tests/unit/Analyser/MetricsTest.php
index 63db362..b016f95 100644
--- a/tests/unit/Analyser/MetricsTest.php
+++ b/tests/unit/Analyser/MetricsTest.php
@@ -39,27 +39,27 @@ protected function setUp(): void
 
     public function testAbstractnessWithNoDependency(): void
     {
-        assertEquals(0, (new Metrics)->abstractness(new DependencyMap));
+        $this->assertEquals(0, (new Metrics())->abstractness(new DependencyMap()));
     }
 
     public function testCountClasses(): void
     {
-        assertEquals(4, $this->metrics->classCount($this->dependencies));
+        $this->assertEquals(4, $this->metrics->classCount($this->dependencies));
     }
 
     public function testCountInterfaces(): void
     {
-        assertEquals(1, $this->metrics->interfaceCount($this->dependencies));
+        $this->assertEquals(1, $this->metrics->interfaceCount($this->dependencies));
     }
 
     public function testCountAbstractClasses(): void
     {
-        assertEquals(1, $this->metrics->abstractClassCount($this->dependencies));
+        $this->assertEquals(1, $this->metrics->abstractClassCount($this->dependencies));
     }
 
     public function testCountTraits(): void
     {
-        assertEquals(1, $this->metrics->traitCount($this->dependencies));
+        $this->assertEquals(1, $this->metrics->traitCount($this->dependencies));
     }
 
     public function testComputeAbstractness(): void
@@ -69,7 +69,7 @@ public function testComputeAbstractness(): void
 
     public function testComputeAfferentCoupling(): void
     {
-        assertEquals([
+        $this->assertEquals([
             'A' => 0,
             'G' => 0,
             'R' => 0,
@@ -83,7 +83,7 @@ public function testComputeAfferentCoupling(): void
     public function testComputeEfferentCoupling(): void
     {
         // all my classes depend only on one dependency
-        assertEquals([
+        $this->assertEquals([
             'A' => 1,
             'G' => 1,
             'R' => 1,
@@ -96,7 +96,7 @@ public function testComputeEfferentCoupling(): void
 
     public function testComputeInstability(): void
     {
-        assertEquals([
+        $this->assertEquals([
             'A' => 1,
             'G' => 1,
             'R' => 1,
diff --git a/tests/unit/Analyser/StaticAnalyserTest.php b/tests/unit/Analyser/StaticAnalyserTest.php
index f3e0e53..cea64e5 100644
--- a/tests/unit/Analyser/StaticAnalyserTest.php
+++ b/tests/unit/Analyser/StaticAnalyserTest.php
@@ -47,7 +47,7 @@ public function testAnalyse(): void
         $phpFile = $this->createMock(PhpFile::class);
         $phpFile->method('code')->willReturn('');
         $dependencies = $this->analyser->analyse((new PhpFileSet())->add($phpFile));
-        assertEquals(new DependencyMap(), $dependencies);
+        $this->assertEquals(new DependencyMap(), $dependencies);
     }
 
     public function testEnrichesExceptionWhenParserThrows(): void
diff --git a/tests/unit/Analyser/XDebugFunctionTraceAnalyserTest.php b/tests/unit/Analyser/XDebugFunctionTraceAnalyserTest.php
index 3e6246d..4507315 100644
--- a/tests/unit/Analyser/XDebugFunctionTraceAnalyserTest.php
+++ b/tests/unit/Analyser/XDebugFunctionTraceAnalyserTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Mihaeu\PhpDependencies\Analyser;
 
@@ -37,7 +39,7 @@ public function testAnalyse(): void
             [0, 1, 2, 3, 4, 'B->c', 6, 7, 8, 9, 10, 'class A'],
             [0, 1, 2, 3, 4, 'D->c', 6, 7, 8, 9, 10, 'class A'],
         ]);
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::map('
                 B --> A
                 D --> A
@@ -58,7 +60,7 @@ public function testAnalyseIgnoresScalarValues(): void
             [0, 1, 2, 3, 4, 'D->c', 6, 7, 8, 9, 10, 'int'],
             [0, 1, 2, 3, 4, 'D->c', 6, 7, 8, 9, 10, 'resource'],
         ]);
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::map('
                 B --> A
             '),
@@ -74,7 +76,7 @@ public function testThrowsExceptionIfFileCannotBeOpened(): void
         $this->xDebugFunctionTraceAnalyser->analyse($tmpFile);
     }
 
-    private function createContent(array $data) : string
+    private function createContent(array $data): string
     {
         return array_reduce($data, function (string $carry, array $lineParts) {
             return $carry.implode("\t", $lineParts).PHP_EOL;
diff --git a/tests/unit/Cli/ApplicationTest.php b/tests/unit/Cli/ApplicationTest.php
index ea25072..1bbc134 100644
--- a/tests/unit/Cli/ApplicationTest.php
+++ b/tests/unit/Cli/ApplicationTest.php
@@ -56,9 +56,9 @@ public function testWarningIfXDebugEnabled(): void
         // not sure how to mock this, so we test only one case, there's always one error message regarding
         // Symfony console setup, so if there's no xdebug loaded we still see one message
         if (!extension_loaded('xdebug')) {
-            $errorOutput->expects(once())->method('writeln');
+            $errorOutput->expects($this->once())->method('writeln');
         } else {
-            $errorOutput->expects(exactly(2))->method('writeln');
+            $errorOutput->expects($this->exactly(2))->method('writeln');
         }
         $this->application->doRun($this->input, $this->output);
     }
@@ -76,9 +76,9 @@ public function testPrintsErrorMessageIfParserThrowsException(): void
         $errorOutput = $this->createMock(ErrorOutput::class);
         $this->application->setErrorOutput($errorOutput);
         if (!extension_loaded('xdebug')) {
-            $errorOutput->expects(once())->method('writeln')->with($expectedMessage);
+            $errorOutput->expects($this->once())->method('writeln')->with($expectedMessage);
         } else {
-            $errorOutput->expects(exactly(2))->method('writeln')->withConsecutive(
+            $errorOutput->expects($this->exactly(2))->method('writeln')->withConsecutive(
                 [self::XDEBUG_WARNING],
                 [$expectedMessage]
             );
@@ -95,7 +95,7 @@ public function testValidatesDsmInput(): void
         $application->setErrorOutput($errorOutput);
 
         $returnCode = $application->doRun($this->input, $this->output);
-        assertEquals(0, $returnCode);
+        $this->assertEquals(0, $returnCode);
     }
 
     public function testValidatesUmlInput(): void
@@ -107,7 +107,7 @@ public function testValidatesUmlInput(): void
         $application->setErrorOutput($errorOutput);
 
         $returnCode = $application->doRun($this->input, $this->output);
-        assertEquals(0, $returnCode);
+        $this->assertEquals(0, $returnCode);
     }
 
     public function testValidatesMetricInput(): void
@@ -119,7 +119,7 @@ public function testValidatesMetricInput(): void
         $application->setErrorOutput($errorOutput);
 
         $returnCode = $application->doRun($this->input, $this->output);
-        assertEquals(0, $returnCode);
+        $this->assertEquals(0, $returnCode);
     }
 
     public function testValidatesDotInput(): void
@@ -131,7 +131,7 @@ public function testValidatesDotInput(): void
         $application->setErrorOutput($errorOutput);
 
         $returnCode = $application->doRun($this->input, $this->output);
-        assertEquals(0, $returnCode);
+        $this->assertEquals(0, $returnCode);
     }
 
     public function testCommandWithHelpOptionProvidesHelpForDotCommand(): void
@@ -149,7 +149,7 @@ public function testNoCommandWithVersionOptionWritesVersion(): void
         $input = new ArgvInput(['', '--version']);
         $output = new BufferedOutput();
         (new Application('Test', '4.2.0', $this->dispatcher))->doRun($input, $output);
-        assertRegExp('/\d+\.\d+\.\d+/', $output->fetch());
+        $this->assertMatchesRegularExpression('/\d+\.\d+\.\d+/', $output->fetch());
     }
 
     public function testNoCommandWithHelpOptionWritesHelp(): void
diff --git a/tests/unit/Cli/DispatcherTest.php b/tests/unit/Cli/DispatcherTest.php
index 9e2c6fa..799ac12 100644
--- a/tests/unit/Cli/DispatcherTest.php
+++ b/tests/unit/Cli/DispatcherTest.php
@@ -53,14 +53,14 @@ protected function setUp(): void
     public function testTriggersOnlyOnNamedConsoleEvents(): void
     {
         $consoleEvent = $this->createMock(ConsoleEvent::class);
-        $consoleEvent->expects(never())->method('getInput');
+        $consoleEvent->expects($this->never())->method('getInput');
         $this->dispatcher->dispatch($consoleEvent, 'other event');
     }
 
     public function testTriggersOnlyOnConsoleEvents(): void
     {
         $consoleEvent = $this->createMock(GenericEvent::class);
-        assertEquals(
+        $this->assertEquals(
             $consoleEvent,
             $this->dispatcher->dispatch(clone $consoleEvent, ConsoleEvents::COMMAND)
         );
@@ -80,9 +80,9 @@ public function testInjectsDependenciesIntoConsoleEvents(): void
         $input->method('getOption')->with('dynamic')->willReturn($traceFile);
         $consoleEvent->method('getInput')->willReturn($input);
 
-        $this->xDebugFunctionTraceAnalyser->expects(once())->method('analyse')->with($traceFile);
-        $command->expects(once())->method('setDependencies');
-        $command->expects(once())->method('setPostProcessors');
+        $this->xDebugFunctionTraceAnalyser->expects($this->once())->method('analyse')->with($traceFile);
+        $command->expects($this->once())->method('setDependencies');
+        $command->expects($this->once())->method('setPostProcessors');
         $this->dispatcher->dispatch(clone $consoleEvent, ConsoleEvents::COMMAND);
     }
 }
diff --git a/tests/unit/Cli/DotCommandTest.php b/tests/unit/Cli/DotCommandTest.php
index c6185f2..77148b8 100644
--- a/tests/unit/Cli/DotCommandTest.php
+++ b/tests/unit/Cli/DotCommandTest.php
@@ -44,7 +44,7 @@ public function testGenerateDot(): void
             'filter-namespace' => null,
             'depth' => 0
         ]);
-        $this->dotWrapper->expects(once())->method('generate');
+        $this->dotWrapper->expects($this->once())->method('generate');
 
         $this->dotCommand->run(
             $this->input,
diff --git a/tests/unit/Cli/DsmCommandTest.php b/tests/unit/Cli/DsmCommandTest.php
index 9a1d195..c54ecce 100644
--- a/tests/unit/Cli/DsmCommandTest.php
+++ b/tests/unit/Cli/DsmCommandTest.php
@@ -57,7 +57,7 @@ public function testPassesDependenciesToFormatter(): void
         $dependencies = DependencyHelper::map('A --> B');
         $this->dsmCommand->setDependencies($dependencies);
 
-        $this->dependencyStructureMatrixFormatter->expects(once())->method('format')->with($dependencies);
+        $this->dependencyStructureMatrixFormatter->expects($this->once())->method('format')->with($dependencies);
         $this->dsmCommand->run($this->input, $this->output);
     }
 
diff --git a/tests/unit/Cli/MetricsCommandTest.php b/tests/unit/Cli/MetricsCommandTest.php
index 9821316..15dc5ef 100644
--- a/tests/unit/Cli/MetricsCommandTest.php
+++ b/tests/unit/Cli/MetricsCommandTest.php
@@ -53,7 +53,7 @@ public function testPrintsMetrics(): void
 
         $output = new BufferedOutput();
         $this->metricsCommand->run($this->input, $output);
-        assertEquals(
+        $this->assertEquals(
             '+--------------------+-------+
 | Classes:           | 1     |
 | Abstract classes:  | 2     |
diff --git a/tests/unit/Cli/TextCommandTest.php b/tests/unit/Cli/TextCommandTest.php
index 58a9ef6..c8e20ca 100644
--- a/tests/unit/Cli/TextCommandTest.php
+++ b/tests/unit/Cli/TextCommandTest.php
@@ -52,7 +52,7 @@ public function testPrintsDependencies(): void
         $this->input->method('getOption')->willReturn(false, 0);
         $this->input->method('getOptions')->willReturn(['internals' => false, 'filter-namespace' => null, 'depth' => 0]);
 
-        $this->output->expects(once())
+        $this->output->expects($this->once())
             ->method('writeln')
             ->with(
                 'A\\a\\1\\ClassA --> B\\a\\1\\ClassB'.PHP_EOL
@@ -75,7 +75,7 @@ public function testPrintsOnlyNamespacedDependencies(): void
         $this->input->method('getArgument')->willReturn([sys_get_temp_dir()]);
         $this->input->method('getOptions')->willReturn(['internals' => false, 'filter-namespace' => null, 'depth' => 1]);
 
-        $this->output->expects(once())
+        $this->output->expects($this->once())
             ->method('writeln')
             ->with(
                 'NamespaceA --> NamespaceB'.PHP_EOL
diff --git a/tests/unit/Cli/UmlCommandTest.php b/tests/unit/Cli/UmlCommandTest.php
index 9197b50..140fc7f 100644
--- a/tests/unit/Cli/UmlCommandTest.php
+++ b/tests/unit/Cli/UmlCommandTest.php
@@ -86,7 +86,7 @@ public function testGenerateUml(): void
             'filter-namespace' => null,
             'depth' => 0
         ]);
-        $this->plantUmlWrapper->expects(once())->method('generate');
+        $this->plantUmlWrapper->expects($this->once())->method('generate');
 
         $this->umlCommand->run(
             $this->input,
diff --git a/tests/unit/Dependencies/ClazzTest.php b/tests/unit/Dependencies/ClazzTest.php
index 8d271ab..d3a9b1e 100644
--- a/tests/unit/Dependencies/ClazzTest.php
+++ b/tests/unit/Dependencies/ClazzTest.php
@@ -18,58 +18,58 @@ class ClazzTest extends TestCase
 {
     public function testAcceptsUtf8Name(): void
     {
-        assertEquals('á', (new Clazz('á'))->toString());
+        $this->assertEquals('á', (new Clazz('á'))->toString());
     }
 
     public function testHasValue(): void
     {
-        assertEquals('Name', new Clazz('Name'));
-        assertEquals('Name', (new Clazz('Name'))->toString());
+        $this->assertEquals('Name', new Clazz('Name'));
+        $this->assertEquals('Name', (new Clazz('Name'))->toString());
     }
 
     public function testNamespace(): void
     {
-        assertEquals(new Namespaze(['A', 'a']), (new Clazz('Name', new Namespaze(['A', 'a'])))->namespaze());
+        $this->assertEquals(new Namespaze(['A', 'a']), (new Clazz('Name', new Namespaze(['A', 'a'])))->namespaze());
     }
 
     public function testToStringWithNamespace(): void
     {
-        assertEquals('A\\a\\ClassA', new Clazz('ClassA', new Namespaze(['A', 'a'])));
+        $this->assertEquals('A\\a\\ClassA', new Clazz('ClassA', new Namespaze(['A', 'a'])));
     }
 
     public function testEquals(): void
     {
-        assertTrue((new Clazz('A'))->equals(new Clazz('A')));
+        $this->assertTrue((new Clazz('A'))->equals(new Clazz('A')));
     }
 
     public function testEqualsIgnoresType(): void
     {
-        assertTrue((new Clazz('A'))->equals(new Interfaze('A')));
+        $this->assertTrue((new Clazz('A'))->equals(new Interfaze('A')));
     }
 
     public function testDetectsIfClassHasNamespace(): void
     {
-        assertTrue((new Clazz('Class', new Namespaze(['A'])))->hasNamespace());
+        $this->assertTrue((new Clazz('Class', new Namespaze(['A'])))->hasNamespace());
     }
 
     public function testDetectsIfClassHasNoNamespace(): void
     {
-        assertFalse((new Clazz('Class'))->hasNamespace());
+        $this->assertFalse((new Clazz('Class'))->hasNamespace());
     }
 
     public function testDepthWithoutNamespaceIsOne(): void
     {
-        assertCount(1, new Clazz('A'));
+        $this->assertCount(1, new Clazz('A'));
     }
 
     public function testDepthWithNamespace(): void
     {
-        assertCount(3, new Clazz('A', new Namespaze(['B', 'C'])));
+        $this->assertCount(3, new Clazz('A', new Namespaze(['B', 'C'])));
     }
 
     public function testReduceWithDepthZero(): void
     {
-        assertEquals(
+        $this->assertEquals(
             H::clazz('A\\B\\C\\D'),
             H::clazz('A\\B\\C\\D')->reduceToDepth(0)
         );
@@ -77,13 +77,13 @@ public function testReduceWithDepthZero(): void
 
     public function testReduceToDepthTwoWithoutNamespacesProducesClass(): void
     {
-        assertEquals(new Clazz('A'), (new Clazz('A'))->reduceToDepth(2));
+        $this->assertEquals(new Clazz('A'), (new Clazz('A'))->reduceToDepth(2));
     }
 
     public function testReduceDepthToTwoProducesTopTwoNamespaces(): void
     {
         $clazz = H::clazz('A\\B\\C\\D');
-        assertEquals(
+        $this->assertEquals(
             new Namespaze(['A', 'B']),
             $clazz->reduceToDepth(2)
         );
@@ -91,7 +91,7 @@ public function testReduceDepthToTwoProducesTopTwoNamespaces(): void
 
     public function testReduceToDepthOfOneProducesOneNamespace(): void
     {
-        assertEquals(
+        $this->assertEquals(
             new Namespaze(['A']),
             H::clazz('A\\B\\C\\D')->reduceToDepth(1)
         );
@@ -99,7 +99,7 @@ public function testReduceToDepthOfOneProducesOneNamespace(): void
 
     public function testLeftReduceClassWithNamespace(): void
     {
-        assertEquals(
+        $this->assertEquals(
             H::clazz('D'),
             H::clazz('A\\B\\C\\D')->reduceDepthFromLeftBy(3)
         );
@@ -107,7 +107,7 @@ public function testLeftReduceClassWithNamespace(): void
 
     public function testCannotLeftReduceClassWithNamespaceByItsLength(): void
     {
-        assertEquals(
+        $this->assertEquals(
             H::clazz('A\\B\\C\\D'),
             H::clazz('A\\B\\C\\D')->reduceDepthFromLeftBy(4)
         );
@@ -118,12 +118,12 @@ public function testCannotLeftReduceClassWithNamespaceByItsLength(): void
      */
     public function testAcceptsNumbersAsFirstCharacterInName(): void
     {
-        assertEquals('Vendor\\1Sub\\2Factor', new Clazz('2Factor', new Namespaze(['Vendor', '1Sub'])));
+        $this->assertEquals('Vendor\\1Sub\\2Factor', new Clazz('2Factor', new Namespaze(['Vendor', '1Sub'])));
     }
 
     public function testCannotLeftReduceClassWithNamespaceByMoreThanItsLength(): void
     {
-        assertEquals(
+        $this->assertEquals(
             H::clazz('A\\B\\C\\D'),
             H::clazz('A\\B\\C\\D')->reduceDepthFromLeftBy(5)
         );
@@ -131,14 +131,14 @@ public function testCannotLeftReduceClassWithNamespaceByMoreThanItsLength(): voi
 
     public function testDetectsIfInOtherNamespace(): void
     {
-        assertTrue(DependencyHelper::clazz('A\\b\\T\\Test')->inNamespaze(DependencyHelper::namespaze('A\\b')));
-        assertTrue(DependencyHelper::clazz('A\\Test')->inNamespaze(DependencyHelper::namespaze('A')));
-        assertTrue(DependencyHelper::clazz(Collection::class)->inNamespaze(new Namespaze(['Mihaeu', 'PhpDependencies'])));
+        $this->assertTrue(DependencyHelper::clazz('A\\b\\T\\Test')->inNamespaze(DependencyHelper::namespaze('A\\b')));
+        $this->assertTrue(DependencyHelper::clazz('A\\Test')->inNamespaze(DependencyHelper::namespaze('A')));
+        $this->assertTrue(DependencyHelper::clazz(Collection::class)->inNamespaze(new Namespaze(['Mihaeu', 'PhpDependencies'])));
     }
 
     public function testDetectsIfNotInOtherNamespace(): void
     {
-        assertFalse(DependencyHelper::clazz('Global')->inNamespaze(DependencyHelper::namespaze('A\\b\\T')));
+        $this->assertFalse(DependencyHelper::clazz('Global')->inNamespaze(DependencyHelper::namespaze('A\\b\\T')));
     }
 
     public function testThrowsExceptionIfNameNotValid(): void
@@ -150,11 +150,11 @@ public function testThrowsExceptionIfNameNotValid(): void
 
     public function testDetectsIfClassIsNotNamespaced(): void
     {
-        assertFalse((new Clazz('NoNamespace'))->isNamespaced());
+        $this->assertFalse((new Clazz('NoNamespace'))->isNamespaced());
     }
 
     public function testDetectsIfClassIsNamespaced(): void
     {
-        assertTrue((new Clazz('HasNamespace', new Namespaze(['Vendor'])))->isNamespaced());
+        $this->assertTrue((new Clazz('HasNamespace', new Namespaze(['Vendor'])))->isNamespaced());
     }
 }
diff --git a/tests/unit/Dependencies/DependencyFactoryTest.php b/tests/unit/Dependencies/DependencyFactoryTest.php
index 1a02dde..bf231ec 100644
--- a/tests/unit/Dependencies/DependencyFactoryTest.php
+++ b/tests/unit/Dependencies/DependencyFactoryTest.php
@@ -21,7 +21,7 @@ protected function setUp(): void
 
     public function testInvalidClassReturnsNullDependency(): void
     {
-        assertInstanceOf(
+        $this->assertInstanceOf(
             NullDependency::class,
             $this->clazzFactory->createClazzFromStringArray(['/'])
         );
@@ -29,12 +29,12 @@ public function testInvalidClassReturnsNullDependency(): void
 
     public function testCreatesClazzWithEmptyNamespace(): void
     {
-        assertEquals(new Clazz('Test', new Namespaze([])), $this->clazzFactory->createClazzFromStringArray(['Test']));
+        $this->assertEquals(new Clazz('Test', new Namespaze([])), $this->clazzFactory->createClazzFromStringArray(['Test']));
     }
 
     public function testCreateClazzWithNamespace(): void
     {
-        assertEquals(
+        $this->assertEquals(
             new Clazz('Test', new Namespaze(['Mihaeu', 'PhpDependencies'])),
             $this->clazzFactory->createClazzFromStringArray(['Mihaeu', 'PhpDependencies', 'Test'])
         );
@@ -42,16 +42,16 @@ public function testCreateClazzWithNamespace(): void
 
     public function testCreateInterfaze(): void
     {
-        assertEquals(new AbstractClazz('Test', new Namespaze([])), $this->clazzFactory->createAbstractClazzFromStringArray(['Test']));
+        $this->assertEquals(new AbstractClazz('Test', new Namespaze([])), $this->clazzFactory->createAbstractClazzFromStringArray(['Test']));
     }
 
     public function testCreateAbstractClazz(): void
     {
-        assertEquals(new Interfaze('Test', new Namespaze([])), $this->clazzFactory->createInterfazeFromStringArray(['Test']));
+        $this->assertEquals(new Interfaze('Test', new Namespaze([])), $this->clazzFactory->createInterfazeFromStringArray(['Test']));
     }
 
     public function testCreateTrait(): void
     {
-        assertEquals(new Trait_('Test', new Namespaze([])), $this->clazzFactory->createTraitFromStringArray(['Test']));
+        $this->assertEquals(new Trait_('Test', new Namespaze([])), $this->clazzFactory->createTraitFromStringArray(['Test']));
     }
 }
diff --git a/tests/unit/Dependencies/DependencyFilterTest.php b/tests/unit/Dependencies/DependencyFilterTest.php
index 1e5cdc6..d4e0a37 100644
--- a/tests/unit/Dependencies/DependencyFilterTest.php
+++ b/tests/unit/Dependencies/DependencyFilterTest.php
@@ -25,7 +25,7 @@ public function testRemovesInternals(): void
     {
         $dependencies = DependencyHelper::map('From --> To, SplFileInfo');
         $expected = (new DependencyMap())->add(new Clazz('From'), new Clazz('To'));
-        assertEquals($expected, $this->filter->removeInternals($dependencies));
+        $this->assertEquals($expected, $this->filter->removeInternals($dependencies));
     }
 
     public function testFilterByDepthOne(): void
@@ -39,12 +39,12 @@ public function testFilterByDepthOne(): void
             _B --> SplFileInfo
         ');
         $actual = $this->filter->filterByDepth($dependencies, 1);
-        assertEquals($expected, $actual);
+        $this->assertEquals($expected, $actual);
     }
 
     public function testMapUnderscoreNamespaces(): void
     {
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::map('
                 A\\b\\c --> D\\e\\f
                 F\\a --> D\\b
@@ -58,7 +58,7 @@ public function testMapUnderscoreNamespaces(): void
 
     public function testMapUnderscoreNamespacesAlreadyNamespace(): void
     {
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::map('
                 VendorA\\Tests\\DDC1209_1 --> a\\To
                 A\\__b__\\c --> D\\e\\f
@@ -77,7 +77,7 @@ public function testFilterByDepthThree(): void
         ');
         $expected = DependencyHelper::map('_VendorA\\ProjectA\\PathA --> _VendorB\\ProjectB\\PathB');
         $actual = $this->filter->filterByDepth($dependencies, 3);
-        assertEquals($expected, $actual);
+        $this->assertEquals($expected, $actual);
     }
 
     public function testFilterByVendor(): void
@@ -90,7 +90,7 @@ public function testFilterByVendor(): void
         $expected = DependencyHelper::map('
             VendorA\\A --> VendorA\\C
         ');
-        assertEquals($expected, $this->filter->filterByNamespace($dependencies, 'VendorA'));
+        $this->assertEquals($expected, $this->filter->filterByNamespace($dependencies, 'VendorA'));
     }
 
     public function testFilterByDepth0ReturnsEqual(): void
@@ -101,7 +101,7 @@ public function testFilterByDepth0ReturnsEqual(): void
             VendorB\\B --> VendorA\\A
             VendorC\\C --> VendorA\\A
         ');
-        assertEquals($dependencies, $this->filter->filterByDepth($dependencies, 0));
+        $this->assertEquals($dependencies, $this->filter->filterByDepth($dependencies, 0));
     }
     public function testRemoveClasses(): void
     {
@@ -114,12 +114,12 @@ public function testRemoveClasses(): void
             VendorB\\B --> VendorA\\A
             VendorC\\C --> B
         '));
-        assertEquals($expected, $actual);
+        $this->assertEquals($expected, $actual);
     }
 
     public function testFilterFromDependencies(): void
     {
-        assertEquals(DependencyHelper::map('
+        $this->assertEquals(DependencyHelper::map('
             Good\\A --> Bad\\B
             Good\\B --> Good\\C
         '), $this->filter->filterByFromNamespace(DependencyHelper::map('
@@ -166,12 +166,12 @@ public function testRunAllFilters(): void
             A\\a\\z --> A\\b\\z
             A\\b\\c --> A\\b\\z
         ');
-        assertEquals($expected, $actual);
+        $this->assertEquals($expected, $actual);
     }
 
     public function testExcludeByRegex(): void
     {
-        assertEquals(DependencyHelper::map('
+        $this->assertEquals(DependencyHelper::map('
             X --> Z
         '), $this->filter->excludeByRegex(DependencyHelper::map('
             Test\\A --> B
@@ -186,6 +186,6 @@ public function testExcludeByRegex(): void
     public function testPostFilters(): void
     {
         $filters = $this->filter->postFiltersByOptions(['no-classes' => true, 'depth' => 1]);
-        assertEquals(new Namespaze(['A']), $filters(new Clazz('Test', new Namespaze(['A', 'a']))));
+        $this->assertEquals(new Namespaze(['A']), $filters(new Clazz('Test', new Namespaze(['A', 'a']))));
     }
 }
diff --git a/tests/unit/Dependencies/DependencyMapTest.php b/tests/unit/Dependencies/DependencyMapTest.php
index 1200176..7591c33 100644
--- a/tests/unit/Dependencies/DependencyMapTest.php
+++ b/tests/unit/Dependencies/DependencyMapTest.php
@@ -19,12 +19,12 @@ public function testNoDuplicates(): void
             A --> B
             B --> C
         ');
-        assertEquals($map, $map->add(new Clazz('A'), new Clazz('B')));
+        $this->assertEquals($map, $map->add(new Clazz('A'), new Clazz('B')));
     }
 
     public function testAddMapToMap(): void
     {
-        assertEquals(DependencyHelper::map('
+        $this->assertEquals(DependencyHelper::map('
             A --> B, C
             B --> C
         '), DependencyHelper::map('
@@ -38,7 +38,7 @@ public function testAddMapToMap(): void
     public function testAddMoreDependenciesToExistingPair(): void
     {
         $map = DependencyHelper::map('A --> B');
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::map('A --> B, C, D'),
             $map->addSet(new Clazz('A'), DependencyHelper::dependencySet('C, D'))
         );
@@ -46,14 +46,14 @@ public function testAddMoreDependenciesToExistingPair(): void
 
     public function testDoesNotAcceptDependenciesMappingToThemselves(): void
     {
-        assertCount(0, DependencyHelper::map('')->add(new Clazz('A'), new Clazz('A')));
+        $this->assertCount(0, DependencyHelper::map('')->add(new Clazz('A'), new Clazz('A')));
     }
 
     public function testReturnsTrueIfAnyMatches(): void
     {
         $toSet = DependencyHelper::dependencySet('To, ToAnother');
         $dependencies = (new DependencyMap())->addSet(new Clazz('Test'), $toSet);
-        assertTrue($dependencies->any(function (Dependency $from, Dependency $to) use ($toSet) {
+        $this->assertTrue($dependencies->any(function (Dependency $from, Dependency $to) use ($toSet) {
             return $toSet->contains($to);
         }));
     }
@@ -61,7 +61,7 @@ public function testReturnsTrueIfAnyMatches(): void
     public function testReturnsTrueIfNoneMatches(): void
     {
         $dependencies = (new DependencyMap())->addSet(new Clazz('Test'), DependencyHelper::dependencySet('To, ToAnother'));
-        assertTrue($dependencies->none(function (Dependency $from, Dependency $to) {
+        $this->assertTrue($dependencies->none(function (Dependency $from, Dependency $to) {
             return $from === new Clazz('Other');
         }));
     }
@@ -69,14 +69,14 @@ public function testReturnsTrueIfNoneMatches(): void
     public function testEach(): void
     {
         DependencyHelper::map('From --> To, ToAnother')->each(function (Dependency $from, Dependency $to) {
-            assertTrue($from->equals(new Clazz('From')));
+            $this->assertTrue($from->equals(new Clazz('From')));
         });
     }
 
     public function testReduce(): void
     {
         $dependencies = DependencyHelper::map('From --> To, ToAnother');
-        assertEquals('ToToAnother', $dependencies->reduce('', function (string $output, Dependency $from, Dependency $to) {
+        $this->assertEquals('ToToAnother', $dependencies->reduce('', function (string $output, Dependency $from, Dependency $to) {
             return $output.$to->toString();
         }));
     }
@@ -85,19 +85,19 @@ public function testFromClasses(): void
     {
         $dependencies = DependencyHelper::map('From --> To, ToAnother');
         $expected = (new DependencySet())->add(new Clazz('From'));
-        assertEquals($expected, $dependencies->fromDependencies());
+        $this->assertEquals($expected, $dependencies->fromDependencies());
     }
 
     public function testAllClasses(): void
     {
         $dependencies = DependencyHelper::map('From --> To, ToAnother');
         $expected = DependencyHelper::dependencySet('From, To, ToAnother');
-        assertEquals($expected, $dependencies->allDependencies());
+        $this->assertEquals($expected, $dependencies->allDependencies());
     }
 
     public function testToString(): void
     {
-        assertEquals(
+        $this->assertEquals(
             'VendorA\\A --> VendorB\\A'.PHP_EOL
             .'VendorA\\A --> VendorA\\C'.PHP_EOL
             .'VendorB\\B --> VendorA\\A'.PHP_EOL
@@ -112,7 +112,7 @@ public function testToString(): void
 
     public function testMapToArray(): void
     {
-        assertEquals([new Clazz('A'), new Clazz('C')], DependencyHelper::map('
+        $this->assertEquals([new Clazz('A'), new Clazz('C')], DependencyHelper::map('
             A --> B
             C --> D
         ')->mapToArray(function (Dependency $from, Dependency $to) {
@@ -122,7 +122,7 @@ public function testMapToArray(): void
 
     public function testToArray(): void
     {
-        assertEquals([
+        $this->assertEquals([
             'A' => [
                 'key'   => new Clazz('A'),
                 'value' => (new DependencySet())->add(new Clazz('B')),
@@ -139,7 +139,7 @@ public function testToArray(): void
 
     public function testFilter(): void
     {
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::map('A --> B'),
             DependencyHelper::map('
                 A --> B
@@ -152,7 +152,7 @@ public function testFilter(): void
 
     public function testCount(): void
     {
-        assertCount(2, DependencyHelper::map('
+        $this->assertCount(2, DependencyHelper::map('
             A --> B, C, D
             D --> E
         '));
@@ -168,12 +168,12 @@ public function testEquals(): void
             A --> B, C, D
             D --> E
         ')->add(new Clazz('D'), new Clazz('E'));
-        assertTrue($one->equals($two));
+        $this->assertTrue($one->equals($two));
     }
 
     public function testContainsIsTrueIfItMatchesTheKey(): void
     {
-        assertTrue(DependencyHelper::map('
+        $this->assertTrue(DependencyHelper::map('
             A --> B, C, D
             D --> E
         ')->contains(new Clazz('A')));
@@ -181,7 +181,7 @@ public function testContainsIsTrueIfItMatchesTheKey(): void
 
     public function testContainsIsFalseIfItOnlyMatchesTheValue(): void
     {
-        assertFalse(DependencyHelper::map('
+        $this->assertFalse(DependencyHelper::map('
             A --> B, C, D
             D --> E
         ')->contains(new Clazz('E')));
@@ -193,14 +193,14 @@ public function testMapAllDependencies(): void
             A\b --> C
             Y --> Z\d
         ');
-        assertEquals(DependencyHelper::dependencySet('_A, _Z'), $map->mapAllDependencies(function (Dependency $dependency) {
+        $this->assertEquals(DependencyHelper::dependencySet('_A, _Z'), $map->mapAllDependencies(function (Dependency $dependency) {
             return $dependency->namespaze();
         }));
     }
 
     public function testGet(): void
     {
-        assertEquals(
+        $this->assertEquals(
             DependencyHelper::dependencySet('A, B, C'),
             DependencyHelper::map('D --> A, B, C')->get(new Clazz('D'))
         );
@@ -208,7 +208,7 @@ public function testGet(): void
 
     public function testReduceEachDependency(): void
     {
-        assertEquals(DependencyHelper::map('
+        $this->assertEquals(DependencyHelper::map('
             _A --> _B, _C
         '), DependencyHelper::map('
             A\b --> B\d, C\d
@@ -221,28 +221,28 @@ public function testReduceEachDependency(): void
     public function testDoesNotPrintNullDependenciesInKey(): void
     {
         $map = (new DependencyMap())->add(new NullDependency(), new Clazz('A'));
-        assertEmpty($map->toString());
+        $this->assertEmpty($map->toString());
     }
 
     public function testDoesNotPrintNullDependenciesInValue(): void
     {
         $map = (new DependencyMap())->add(new Clazz('A'), new NullDependency());
-        assertEmpty($map->toString());
+        $this->assertEmpty($map->toString());
     }
 
     public function testCannotAddEmptyNamespaceAsFrom(): void
     {
-        assertEmpty((new DependencyMap())->add(new Clazz('A'), new Namespaze([])));
+        $this->assertEmpty((new DependencyMap())->add(new Clazz('A'), new Namespaze([])));
     }
 
     public function testCannotAddEmptyNamespaceAsTo(): void
     {
-        assertEmpty((new DependencyMap())->add(new Namespaze([]), new Clazz('A')));
+        $this->assertEmpty((new DependencyMap())->add(new Namespaze([]), new Clazz('A')));
     }
 
     public function testCannotAddSelf(): void
     {
-        assertEmpty((new DependencyMap())->add(new Clazz('A'), new Clazz('self')));
+        $this->assertEmpty((new DependencyMap())->add(new Clazz('A'), new Clazz('self')));
     }
 
     public function testCannotAddDependencyToYourself(): void
@@ -256,6 +256,6 @@ public function testCannotAddDependencyToYourself(): void
                 new Clazz('A'),
                 new Clazz('static')
             );
-        assertEmpty($dependencyMap);
+        $this->assertEmpty($dependencyMap);
     }
 }
diff --git a/tests/unit/Dependencies/DependencySetTest.php b/tests/unit/Dependencies/DependencySetTest.php
index 573dcb3..d2ec993 100644
--- a/tests/unit/Dependencies/DependencySetTest.php
+++ b/tests/unit/Dependencies/DependencySetTest.php
@@ -18,7 +18,7 @@ public function testAdd(): void
         $clazzCollection = (new DependencySet())
             ->add(new Clazz('Test'));
         $clazzCollection->each(function (Dependency $clazz) {
-            assertEquals(new Clazz('Test'), $clazz);
+            $this->assertEquals(new Clazz('Test'), $clazz);
         });
     }
 
@@ -27,21 +27,21 @@ public function testIsImmutable(): void
         $clazzCollection = (new DependencySet())
             ->add(new Clazz('Test'));
         $newCollectionAfterRefusingDuplicate = $clazzCollection->add(new Clazz('Test'));
-        assertNotSame($clazzCollection, $newCollectionAfterRefusingDuplicate);
+        $this->assertNotSame($clazzCollection, $newCollectionAfterRefusingDuplicate);
     }
 
     public function testDoesNotAcceptDuplicates(): void
     {
         $clazzCollection = (new DependencySet())
             ->add(new Clazz('Test'));
-        assertEquals($clazzCollection, $clazzCollection->add(new Clazz('Test')));
+        $this->assertEquals($clazzCollection, $clazzCollection->add(new Clazz('Test')));
     }
 
     public function testToArray(): void
     {
         $clazzCollection = (new DependencySet())
             ->add(new Clazz('Test'));
-        assertEquals([new Clazz('Test')], $clazzCollection->toArray());
+        $this->assertEquals([new Clazz('Test')], $clazzCollection->toArray());
     }
 
     public function testToString(): void
@@ -49,34 +49,34 @@ public function testToString(): void
         $clazzCollection = (new DependencySet())
             ->add(new Clazz('Test'))
             ->add(new Clazz('Test2'));
-        assertEquals('Test'.PHP_EOL.'Test2', $clazzCollection->__toString());
+        $this->assertEquals('Test'.PHP_EOL.'Test2', $clazzCollection->__toString());
     }
 
     public function testFilter(): void
     {
         $expected = DependencyHelper::dependencySet('AB, AC');
-        assertEquals($expected, DependencyHelper::dependencySet('AB, AC, BA, CA')->filter(function (Dependency $dependency) {
+        $this->assertEquals($expected, DependencyHelper::dependencySet('AB, AC, BA, CA')->filter(function (Dependency $dependency) {
             return strpos($dependency->toString(), 'A') === 0;
         }));
     }
 
     public function testReduce(): void
     {
-        assertEquals('ABC', DependencyHelper::dependencySet('A, B, C')->reduce('', function (string $carry, Dependency $dependency) {
+        $this->assertEquals('ABC', DependencyHelper::dependencySet('A, B, C')->reduce('', function (string $carry, Dependency $dependency) {
             return $carry.$dependency->toString();
         }));
     }
 
     public function testNoneIsTrueWhenNoneMatches(): void
     {
-        assertTrue(DependencyHelper::dependencySet('AB, AC, BA, CA')->none(function (Dependency $dependency) {
+        $this->assertTrue(DependencyHelper::dependencySet('AB, AC, BA, CA')->none(function (Dependency $dependency) {
             return strpos($dependency->toString(), 'D') === 0;
         }));
     }
 
     public function testNoneIsFalseWhenSomeMatch(): void
     {
-        assertFalse(DependencyHelper::dependencySet('AB, AC, BA, CA')->none(function (Dependency $dependency) {
+        $this->assertFalse(DependencyHelper::dependencySet('AB, AC, BA, CA')->none(function (Dependency $dependency) {
             return strpos($dependency->toString(), 'A') === 0;
         }));
     }
diff --git a/tests/unit/Dependencies/NamespazeTest.php b/tests/unit/Dependencies/NamespazeTest.php
index 09b4e41..52fa4f6 100644
--- a/tests/unit/Dependencies/NamespazeTest.php
+++ b/tests/unit/Dependencies/NamespazeTest.php
@@ -14,12 +14,12 @@ class NamespazeTest extends TestCase
 {
     public function testAcceptsEmptyNamespace(): void
     {
-        assertEquals('', new Namespaze([]));
+        $this->assertEquals('', new Namespaze([]));
     }
 
     public function testAcceptsValidNamespaceParts(): void
     {
-        assertEquals('a\b\c', new Namespaze(['a', 'b', 'c']));
+        $this->assertEquals('a\b\c', new Namespaze(['a', 'b', 'c']));
     }
 
     public function testDetectsInvalidNamespaceParts(): void
@@ -30,78 +30,78 @@ public function testDetectsInvalidNamespaceParts(): void
 
     public function testDepthOfEmptyNamespaceIsZero(): void
     {
-        assertCount(0, new Namespaze([]));
+        $this->assertCount(0, new Namespaze([]));
     }
 
     public function testDepthOfNamespace(): void
     {
-        assertCount(2, new Namespaze(['A', 'B']));
+        $this->assertCount(2, new Namespaze(['A', 'B']));
     }
 
     public function testReducingDepthLowerThanPossibleProducesNullDependency(): void
     {
-        assertInstanceOf(NullDependency::class, (new Namespaze(['Test']))->reduceToDepth(3));
+        $this->assertInstanceOf(NullDependency::class, (new Namespaze(['Test']))->reduceToDepth(3));
     }
 
     public function testReduceToMaxDepth(): void
     {
-        assertEquals(new Namespaze(['A', 'B']), (new Namespaze(['A', 'B', 'C', 'D']))->reduceToDepth(2));
+        $this->assertEquals(new Namespaze(['A', 'B']), (new Namespaze(['A', 'B', 'C', 'D']))->reduceToDepth(2));
     }
 
     public function testDoNotReduceForMaxDepthZero(): void
     {
-        assertEquals(new Namespaze(['A', 'B']), (new Namespaze(['A', 'B']))->reduceToDepth(0));
+        $this->assertEquals(new Namespaze(['A', 'B']), (new Namespaze(['A', 'B']))->reduceToDepth(0));
     }
 
     public function testLeftReduceNamespace(): void
     {
-        assertEquals(new Namespaze(['C']), (new Namespaze(['A', 'B', 'C']))->reduceDepthFromLeftBy(2));
+        $this->assertEquals(new Namespaze(['C']), (new Namespaze(['A', 'B', 'C']))->reduceDepthFromLeftBy(2));
     }
 
     public function testReduceSameAsLengthProducesEmptyNamespace(): void
     {
-        assertEquals(new Namespaze([]), (new Namespaze(['A', 'B', 'C']))->reduceDepthFromLeftBy(3));
+        $this->assertEquals(new Namespaze([]), (new Namespaze(['A', 'B', 'C']))->reduceDepthFromLeftBy(3));
     }
 
     public function testReduceMoreThanLengthProducesEmptyNamespace(): void
     {
-        assertEquals(new Namespaze([]), (new Namespaze(['A', 'B', 'C']))->reduceDepthFromLeftBy(5));
+        $this->assertEquals(new Namespaze([]), (new Namespaze(['A', 'B', 'C']))->reduceDepthFromLeftBy(5));
     }
 
     public function testEquals(): void
     {
-        assertTrue((new Namespaze(['A', 'B']))->equals(new Namespaze(['A', 'B'])));
-        assertTrue((new Namespaze([]))->equals(new Namespaze([])));
-        assertFalse((new Namespaze(['A', 'B']))->equals(new Namespaze(['A'])));
-        assertFalse((new Namespaze(['A', 'B']))->equals(new Namespaze([])));
+        $this->assertTrue((new Namespaze(['A', 'B']))->equals(new Namespaze(['A', 'B'])));
+        $this->assertTrue((new Namespaze([]))->equals(new Namespaze([])));
+        $this->assertFalse((new Namespaze(['A', 'B']))->equals(new Namespaze(['A'])));
+        $this->assertFalse((new Namespaze(['A', 'B']))->equals(new Namespaze([])));
     }
 
     public function testPartsByIndex(): void
     {
-        assertEquals(new Namespaze(['1']), (new Namespaze(['1', '2']))->parts()[0]);
-        assertEquals(new Namespaze(['2']), (new Namespaze(['1', '2']))->parts()[1]);
+        $this->assertEquals(new Namespaze(['1']), (new Namespaze(['1', '2']))->parts()[0]);
+        $this->assertEquals(new Namespaze(['2']), (new Namespaze(['1', '2']))->parts()[1]);
     }
 
     public function testNamespazeReturnsItself(): void
     {
-        assertEquals(new Namespaze(['1', '2']), (new Namespaze(['1', '2']))->namespaze());
+        $this->assertEquals(new Namespaze(['1', '2']), (new Namespaze(['1', '2']))->namespaze());
     }
 
     public function testDetectsIfInOtherNamespace(): void
     {
-        assertTrue((new Namespaze(['A', 'b', 'T']))->inNamespaze(new Namespaze(['A', 'b', 'T'])));
-        assertTrue((new Namespaze(['A', 'b', 'T']))->inNamespaze(new Namespaze(['A'])));
+        $this->assertTrue((new Namespaze(['A', 'b', 'T']))->inNamespaze(new Namespaze(['A', 'b', 'T'])));
+        $this->assertTrue((new Namespaze(['A', 'b', 'T']))->inNamespaze(new Namespaze(['A'])));
     }
 
     public function testDetectsIfNotInOtherNamespace(): void
     {
-        assertFalse((new Namespaze(['XZY', 'b', 'T']))->inNamespaze(new Namespaze(['A', 'b', 'T'])));
-        assertFalse((new Namespaze([]))->inNamespaze(new Namespaze(['A', 'b', 'T'])));
-        assertFalse((new Namespaze(['XZY', 'b', 'T']))->inNamespaze(new Namespaze([])));
+        $this->assertFalse((new Namespaze(['XZY', 'b', 'T']))->inNamespaze(new Namespaze(['A', 'b', 'T'])));
+        $this->assertFalse((new Namespaze([]))->inNamespaze(new Namespaze(['A', 'b', 'T'])));
+        $this->assertFalse((new Namespaze(['XZY', 'b', 'T']))->inNamespaze(new Namespaze([])));
     }
 
     public function testEmptyNamespaceIsNotNamespaced(): void
     {
-        assertFalse((new Namespaze([]))->isNamespaced());
+        $this->assertFalse((new Namespaze([]))->isNamespaced());
     }
 }
diff --git a/tests/unit/Dependencies/NullDependencyTest.php b/tests/unit/Dependencies/NullDependencyTest.php
index dc60cc7..1330fcf 100644
--- a/tests/unit/Dependencies/NullDependencyTest.php
+++ b/tests/unit/Dependencies/NullDependencyTest.php
@@ -13,46 +13,46 @@ class NullDependencyTest extends TestCase
 {
     public function testReduceToDepth(): void
     {
-        assertEquals(new NullDependency(), (new NullDependency())->reduceToDepth(99));
+        $this->assertEquals(new NullDependency(), (new NullDependency())->reduceToDepth(99));
     }
 
     public function testReduceDepthFromLeftBy(): void
     {
-        assertEquals(new NullDependency(), (new NullDependency())->reduceDepthFromLeftBy(99));
+        $this->assertEquals(new NullDependency(), (new NullDependency())->reduceDepthFromLeftBy(99));
     }
 
     public function testEquals(): void
     {
-        assertFalse((new NullDependency())->equals(new NullDependency()));
+        $this->assertFalse((new NullDependency())->equals(new NullDependency()));
     }
 
     public function testToString(): void
     {
-        assertEquals('', (new NullDependency())->__toString());
+        $this->assertEquals('', (new NullDependency())->__toString());
     }
 
     public function testNamespaze(): void
     {
-        assertEquals(new Namespaze([]), (new NullDependency())->namespaze());
+        $this->assertEquals(new Namespaze([]), (new NullDependency())->namespaze());
     }
 
     public function testInNamespazeIsFalseForEmptyNamespace(): void
     {
-        assertFalse((new NullDependency())->inNamespaze(new Namespaze([])));
+        $this->assertFalse((new NullDependency())->inNamespaze(new Namespaze([])));
     }
 
     public function testInNamespazeIsFalseForEveryNamespace(): void
     {
-        assertFalse((new NullDependency())->inNamespaze(new Namespaze(['A'])));
+        $this->assertFalse((new NullDependency())->inNamespaze(new Namespaze(['A'])));
     }
 
     public function testCountIsAlwaysZero(): void
     {
-        assertCount(0, new NullDependency());
+        $this->assertCount(0, new NullDependency());
     }
 
     public function testIsNotNamespaced(): void
     {
-        assertFalse((new NullDependency())->isNamespaced());
+        $this->assertFalse((new NullDependency())->isNamespaced());
     }
 }
diff --git a/tests/unit/DependencyHelper.php b/tests/unit/DependencyHelper.php
index 29b1b3d..8aa9829 100644
--- a/tests/unit/DependencyHelper.php
+++ b/tests/unit/DependencyHelper.php
@@ -27,7 +27,7 @@ class DependencyHelper
      *
      * @throws InvalidArgumentException
      */
-    public static function map(string $input) : DependencyMap
+    public static function map(string $input): DependencyMap
     {
         $lines = preg_split('/\v+/', $input, -1, PREG_SPLIT_NO_EMPTY);
         $array_reduce = array_reduce(
@@ -59,7 +59,7 @@ public static function clazz(string $input): Dependency
      *
      * @return Namespaze
      */
-    public static function namespaze(string $input) : Namespaze
+    public static function namespaze(string $input): Namespaze
     {
         return new Namespaze(explode('\\', $input));
     }
@@ -69,7 +69,7 @@ public static function namespaze(string $input) : Namespaze
      *
      * @return array
      */
-    public static function dependencyPair(string $input) : array
+    public static function dependencyPair(string $input): array
     {
         $tokens = explode('-->', str_replace(' ', '', $input));
         return [self::dependency($tokens[0]), self::dependencySet($tokens[1])];
@@ -80,7 +80,7 @@ public static function dependencyPair(string $input) : array
      *
      * @return DependencySet
      */
-    public static function dependencySet(string $input) : DependencySet
+    public static function dependencySet(string $input): DependencySet
     {
         $set = new DependencySet();
         if ($input === '_') {
@@ -93,7 +93,7 @@ public static function dependencySet(string $input) : DependencySet
         return $set;
     }
 
-    private static function dependency(string $input) : Dependency
+    private static function dependency(string $input): Dependency
     {
         $input = str_replace(' ', '', $input);
         if (strpos($input, '_') === 0) {
diff --git a/tests/unit/DependencyHelperTest.php b/tests/unit/DependencyHelperTest.php
index 7c202b9..13d9107 100644
--- a/tests/unit/DependencyHelperTest.php
+++ b/tests/unit/DependencyHelperTest.php
@@ -24,7 +24,7 @@ public function testConvert(): void
             new Clazz('DepC', new Namespaze(['C'])),
             new Clazz('DepD', new Namespaze(['D']))
         );
-        assertEquals($expected, DependencyHelper::map('
+        $this->assertEquals($expected, DependencyHelper::map('
             A\\DepA --> B\\DepB
             C\\DepC --> D\\DepD
         '));
@@ -39,7 +39,7 @@ public function testConvertMultipleDependencies(): void
             new Clazz('DepA', new Namespaze(['A'])),
             new Clazz('DepD', new Namespaze(['D']))
         );
-        assertEquals($expected, DependencyHelper::map('
+        $this->assertEquals($expected, DependencyHelper::map('
             A\\DepA --> B\\DepB, D\\DepD
         '));
     }
diff --git a/tests/unit/Formatters/DependencyStructureMatrixBuilderTest.php b/tests/unit/Formatters/DependencyStructureMatrixBuilderTest.php
index 93cf730..7a89196 100644
--- a/tests/unit/Formatters/DependencyStructureMatrixBuilderTest.php
+++ b/tests/unit/Formatters/DependencyStructureMatrixBuilderTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Mihaeu\PhpDependencies\Formatters;
 
@@ -27,7 +29,7 @@ public function testBuildMatrixFromClassesWithoutNamespaces(): void
             C --> A
             D --> B
         ');
-        assertEquals([
+        $this->assertEquals([
             'A' => ['A' => 0, 'B' => 0, 'C' => 1, 'D' => 0],
             'B' => ['A' => 1, 'B' => 0, 'C' => 0, 'D' => 1],
             'C' => ['A' => 0, 'B' => 0, 'C' => 0, 'D' => 0],
@@ -43,7 +45,7 @@ public function testBuildMatrixFromClassesWithNamespaces(): void
             CC\\C --> AA\\A
             DD\\D --> BB\\B
         ');
-        assertEquals([
+        $this->assertEquals([
             'AA\\A' => ['AA\\A' => 0, 'BB\\B' => 0, 'CC\\C' => 1, 'DD\\D' => 0],
             'BB\\B' => ['AA\\A' => 1, 'BB\\B' => 0, 'CC\\C' => 0, 'DD\\D' => 1],
             'CC\\C' => ['AA\\A' => 0, 'BB\\B' => 0, 'CC\\C' => 0, 'DD\\D' => 0],
diff --git a/tests/unit/Formatters/DotFormatterTest.php b/tests/unit/Formatters/DotFormatterTest.php
index 5c9b2b8..e0b8a42 100644
--- a/tests/unit/Formatters/DotFormatterTest.php
+++ b/tests/unit/Formatters/DotFormatterTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Mihaeu\PhpDependencies\Formatters;
 
@@ -19,7 +21,7 @@ public function testFormatsSimpleDependencies(): void
             .'}'
         ;
 
-        assertEquals($expected, (new DotFormatter())->format(DependencyHelper::map('
+        $this->assertEquals($expected, (new DotFormatter())->format(DependencyHelper::map('
             A --> B
             C --> D
             A\\b --> D\\c
diff --git a/tests/unit/Formatters/PlantUmlFormatterTest.php b/tests/unit/Formatters/PlantUmlFormatterTest.php
index 7d155e7..9f95c9e 100644
--- a/tests/unit/Formatters/PlantUmlFormatterTest.php
+++ b/tests/unit/Formatters/PlantUmlFormatterTest.php
@@ -23,7 +23,7 @@ protected function setUp(): void
     public function testFormat(): void
     {
         $dependencyCollection = DependencyHelper::map('ClassA --> ClassB, ClassC');
-        assertEquals("@startuml\n\n"
+        $this->assertEquals("@startuml\n\n"
             ."ClassA --|> ClassB\n"
             ."ClassA --|> ClassC\n"
             .'@enduml', $this->plantUmlFormatter->format($dependencyCollection));
@@ -31,7 +31,7 @@ public function testFormat(): void
 
     public function testFormatsNestedNamespaces(): void
     {
-        assertEquals('@startuml
+        $this->assertEquals('@startuml
 namespace A {
 namespace b {
 }
diff --git a/tests/unit/OS/DotWrapperTest.php b/tests/unit/OS/DotWrapperTest.php
index 9844f07..caa0b2e 100644
--- a/tests/unit/OS/DotWrapperTest.php
+++ b/tests/unit/OS/DotWrapperTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Mihaeu\PhpDependencies\OS;
 
@@ -45,7 +47,7 @@ public function testRunsDot(): void
         $root = vfsStream::setup()->url();
 
         $this->shellWrapper
-            ->expects(exactly(2))
+            ->expects($this->exactly(2))
             ->method('run')
             ->withConsecutive(
                 ['dot -V'],
@@ -59,9 +61,9 @@ public function testKeepsDotFiles(): void
     {
         $root = vfsStream::setup()->url();
         $testFile = new SplFileInfo($root.'/test');
-        assertFileNotExists($testFile->getPathname());
+        $this->assertFileDoesNotExist($testFile->getPathname());
         $this->dotWrapper->generate(new DependencyMap(), new SplFileInfo($testFile->getPathname()), true);
-        assertFileExists($testFile->getPathname());
+        $this->assertFileExists($testFile->getPathname());
     }
 
 
@@ -70,6 +72,6 @@ public function testRemovesDotFiles(): void
         $root = vfsStream::setup()->url();
         $testFile = new SplFileInfo($root.'/test');
         $this->dotWrapper->generate(new DependencyMap(), new SplFileInfo($root.'/test.png'), false);
-        assertFileNotExists($testFile->getPathname());
+        $this->assertFileDoesNotExist($testFile->getPathname());
     }
 }
diff --git a/tests/unit/OS/PhpFileFinderTest.php b/tests/unit/OS/PhpFileFinderTest.php
index 32174ea..e77423a 100644
--- a/tests/unit/OS/PhpFileFinderTest.php
+++ b/tests/unit/OS/PhpFileFinderTest.php
@@ -31,7 +31,7 @@ public function testFindsSingleFileInFlatStructure(): void
         $dir = new SplFileInfo($mockDir->url());
         $expected = (new PhpFileSet())
             ->add(new PhpFile(new SplFileInfo($mockDir->url().'/root/someFile.php')));
-        assertEquals($expected, $this->finder->find($dir));
+        $this->assertEquals($expected, $this->finder->find($dir));
     }
 
     public function testFindsFilesInDeepStructure(): void
@@ -58,7 +58,7 @@ public function testFindsFilesInDeepStructure(): void
             ->add(new PhpFile(new SplFileInfo($mockDir->url().'/root/dirA/dirB/fileInB.php')))
             ->add(new PhpFile(new SplFileInfo($mockDir->url().'/root/dirA/dirB/fileInB2.php')))
             ->add(new PhpFile(new SplFileInfo($mockDir->url().'/root/dirA/dirB/dirC/fileInC.php')));
-        assertEquals($expected, $this->finder->find($dir));
+        $this->assertEquals($expected, $this->finder->find($dir));
     }
 
     public function testFindsNothingIfThereIsNothing(): void
@@ -79,7 +79,7 @@ public function testFindsNothingIfThereIsNothing(): void
             ],
         ]);
         $dir = new SplFileInfo($mockDir->url());
-        assertEmpty($this->finder->find($dir));
+        $this->assertEmpty($this->finder->find($dir));
     }
 
     public function testFindFilesInDeeplyNestedDirectory(): void
@@ -108,6 +108,6 @@ public function testFindFilesInDeeplyNestedDirectory(): void
             $mockDir->url().'/root/dirA',
             $mockDir->url().'/root/dirB',
         ]);
-        assertEquals($expected, $actual);
+        $this->assertEquals($expected, $actual);
     }
 }
diff --git a/tests/unit/OS/PhpFileSetTest.php b/tests/unit/OS/PhpFileSetTest.php
index 78bff0a..b269cdd 100644
--- a/tests/unit/OS/PhpFileSetTest.php
+++ b/tests/unit/OS/PhpFileSetTest.php
@@ -20,7 +20,7 @@ public function testEquals(): void
             ->add($file);
         $collection2 = (new PhpFileSet())
             ->add($file);
-        assertTrue($collection1->equals($collection2));
+        $this->assertTrue($collection1->equals($collection2));
     }
 
     public function testDoesNotAllowDuplicated(): void
@@ -28,7 +28,7 @@ public function testDoesNotAllowDuplicated(): void
         $set = (new PhpFileSet())
             ->add(new PhpFile(new SplFileInfo(__DIR__)))
             ->add(new PhpFile(new SplFileInfo(__DIR__)));
-        assertCount(1, $set);
+        $this->assertCount(1, $set);
     }
 
     public function testIsImmutable(): void
@@ -36,7 +36,7 @@ public function testIsImmutable(): void
         $set = (new PhpFileSet())
             ->add(new PhpFile(new SplFileInfo(__DIR__)));
         $setAfterRefusingDuplicate = $set->add(new PhpFile(new SplFileInfo(__DIR__)));
-        assertNotSame($set, $setAfterRefusingDuplicate);
+        $this->assertNotSame($set, $setAfterRefusingDuplicate);
     }
 
     public function testNotEquals(): void
@@ -45,18 +45,18 @@ public function testNotEquals(): void
             ->add(new PhpFile(new SplFileInfo(sys_get_temp_dir())));
         $collection2 = (new PhpFileSet())
             ->add(new PhpFile(new SplFileInfo(__DIR__)));
-        assertFalse($collection1->equals($collection2));
+        $this->assertFalse($collection1->equals($collection2));
     }
 
     public function testCount0WhenEmpty(): void
     {
         $collection1 = new PhpFileSet();
-        assertCount(0, $collection1);
+        $this->assertCount(0, $collection1);
     }
 
     public function testCount(): void
     {
-        assertCount(2, (new PhpFileSet())
+        $this->assertCount(2, (new PhpFileSet())
             ->add(new PhpFile(new SplFileInfo(__DIR__)))
             ->add(new PhpFile(new SplFileInfo(__DIR__.'/../../../composer.json'))));
     }
@@ -65,7 +65,7 @@ public function testEach(): void
     {
         $collection1 = (new PhpFileSet())->add(new PhpFile(new SplFileInfo(__DIR__)));
         $collection1->each(function (PhpFile $file) {
-            assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $file);
+            $this->assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $file);
         });
     }
 
@@ -75,8 +75,8 @@ public function testMapToArray(): void
             ->add(new PhpFile(new SplFileInfo(__DIR__)))
             ->add(new PhpFile(new SplFileInfo(__FILE__)))
             ->toArray();
-        assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $collection1[0]);
-        assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $collection1[1]);
+        $this->assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $collection1[0]);
+        $this->assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $collection1[1]);
     }
 
     public function testAddAll(): void
@@ -86,8 +86,8 @@ public function testAddAll(): void
             ->add(new PhpFile(new SplFileInfo(__DIR__)))
             ->add(new PhpFile(new SplFileInfo(__FILE__)));
         $combinedCollection = $collection1->addAll($collection2)->toArray();
-        assertCount(2, $combinedCollection);
-        assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $combinedCollection[0]);
-        assertEquals(new PhpFile(new SplFileInfo(__FILE__)), $combinedCollection[1]);
+        $this->assertCount(2, $combinedCollection);
+        $this->assertEquals(new PhpFile(new SplFileInfo(__DIR__)), $combinedCollection[0]);
+        $this->assertEquals(new PhpFile(new SplFileInfo(__FILE__)), $combinedCollection[1]);
     }
 }
diff --git a/tests/unit/OS/PhpFileTest.php b/tests/unit/OS/PhpFileTest.php
index 3d1e069..fb6a379 100644
--- a/tests/unit/OS/PhpFileTest.php
+++ b/tests/unit/OS/PhpFileTest.php
@@ -22,14 +22,14 @@ public function testEquals(): void
     {
         $file1 = new PhpFile(new SplFileInfo(sys_get_temp_dir()));
         $file2 = new PhpFile(new SplFileInfo(sys_get_temp_dir()));
-        assertTrue($file1->equals($file2));
+        $this->assertTrue($file1->equals($file2));
     }
 
     public function testNotEquals(): void
     {
         $file1 = new PhpFile(new SplFileInfo(sys_get_temp_dir()));
         $file2 = new PhpFile(new SplFileInfo(__DIR__));
-        assertFalse($file1->equals($file2));
+        $this->assertFalse($file1->equals($file2));
     }
 
     public function testReturnsCode(): void
@@ -39,7 +39,7 @@ public function testReturnsCode(): void
             'someFile.php' => $code,
         ]);
         $file = new PhpFile(new SplFileInfo($mockDir->url().'/someFile.php'));
-        assertEquals($code, $file->code());
+        $this->assertEquals($code, $file->code());
     }
 
     public function testToString(): void
diff --git a/tests/unit/OS/PlantUmlWrapperTest.php b/tests/unit/OS/PlantUmlWrapperTest.php
index b32db55..b98e61b 100644
--- a/tests/unit/OS/PlantUmlWrapperTest.php
+++ b/tests/unit/OS/PlantUmlWrapperTest.php
@@ -41,14 +41,14 @@ public function testDetectsIfPlantUmlIsNotInstalled(): void
     public function testDetectsIfPlantUmlIsInstalled(): void
     {
         $this->shellWrapper->method('run')->willReturn(0);
-        assertInstanceOf(PlantUmlWrapper::class, new PlantUmlWrapper($this->plantUmlFormatter, $this->shellWrapper));
+        $this->assertInstanceOf(PlantUmlWrapper::class, new PlantUmlWrapper($this->plantUmlFormatter, $this->shellWrapper));
     }
 
     public function testGenerate(): void
     {
         $plantUml = new PlantUmlWrapper($this->plantUmlFormatter, $this->shellWrapper);
         $plantUml->generate(new DependencyMap(), new SplFileInfo(sys_get_temp_dir().'/dependencies.png'), true);
-        assertFileExists(sys_get_temp_dir().'/dependencies.uml');
+        $this->assertFileExists(sys_get_temp_dir().'/dependencies.uml');
         unlink(sys_get_temp_dir().'/dependencies.uml');
     }
 
@@ -56,6 +56,6 @@ public function testRemoveUml(): void
     {
         $plantUml = new PlantUmlWrapper($this->plantUmlFormatter, $this->shellWrapper);
         $plantUml->generate(new DependencyMap(), new SplFileInfo(sys_get_temp_dir().'/dependencies.png'));
-        assertFileNotExists(sys_get_temp_dir().'/dependencies.uml');
+        $this->assertFileDoesNotExist(sys_get_temp_dir().'/dependencies.uml');
     }
 }
diff --git a/tests/unit/OS/ShellWrapperTest.php b/tests/unit/OS/ShellWrapperTest.php
index e8f05d6..7a5bab4 100644
--- a/tests/unit/OS/ShellWrapperTest.php
+++ b/tests/unit/OS/ShellWrapperTest.php
@@ -16,11 +16,11 @@ class ShellWrapperTest extends TestCase
      */
     public function testDetectsEcho(): void
     {
-        assertEquals(0, (new ShellWrapper())->run('echo'));
+        $this->assertEquals(0, (new ShellWrapper())->run('echo'));
     }
 
     public function testDetectsWhenApplicationNotInstalled(): void
     {
-        assertNotEquals(0, (new ShellWrapper())->run('xjcsajhckjsdfhksdf'));
+        $this->assertNotEquals(0, (new ShellWrapper())->run('xjcsajhckjsdfhksdf'));
     }
 }
diff --git a/tests/unit/Util/DependencyContainerTest.php b/tests/unit/Util/DependencyContainerTest.php
index ae23367..c73b9a6 100644
--- a/tests/unit/Util/DependencyContainerTest.php
+++ b/tests/unit/Util/DependencyContainerTest.php
@@ -25,7 +25,7 @@ public function provideMethods(): array
             if (!$method->hasReturnType()) {
                 continue;
             }
-            $methods[] = [$method->getName(), (string) $method->getReturnType()];
+            $methods[] = [$method->getName(), $method->getReturnType()->getName()];
         }
         return $methods;
     }
@@ -37,6 +37,6 @@ public function provideMethods(): array
      */
     public function testCanInstantiateAllDependencies(string $methodName, string $expectedReturnType): void
     {
-        assertInstanceOf($expectedReturnType, (new DependencyContainer([]))->{$methodName}());
+        $this->assertInstanceOf($expectedReturnType, (new DependencyContainer([]))->{$methodName}());
     }
 }
diff --git a/tests/unit/Util/FunctionalTest.php b/tests/unit/Util/FunctionalTest.php
index 66d330e..56d8d56 100644
--- a/tests/unit/Util/FunctionalTest.php
+++ b/tests/unit/Util/FunctionalTest.php
@@ -19,7 +19,7 @@ public function testCompose(): void
         $multiplyByTwo = function ($x) {
             return $x * 2;
         };
-        assertEquals(8, Functional::compose(
+        $this->assertEquals(8, Functional::compose(
             $incrementByOne,
             $multiplyByTwo,
             $multiplyByTwo
@@ -28,6 +28,6 @@ public function testCompose(): void
 
     public function testComposeWithoutArgumentsReturnsId(): void
     {
-        assertEquals(9, Functional::compose()(9));
+        $this->assertEquals(9, Functional::compose()(9));
     }
 }
diff --git a/tests/unit/Util/UtilTest.php b/tests/unit/Util/UtilTest.php
index 4f04b7d..750c943 100644
--- a/tests/unit/Util/UtilTest.php
+++ b/tests/unit/Util/UtilTest.php
@@ -13,28 +13,28 @@ class UtilTest extends TestCase
 {
     public function testArrayMatchesAtLeastOnce(): void
     {
-        assertTrue(Util::array_once([1, 2, 3, 'tt'], function ($value, $index) {
+        $this->assertTrue(Util::array_once([1, 2, 3, 'tt'], function ($value, $index) {
             return $value === 'tt';
         }));
     }
 
     public function testArrayMatchesIndex(): void
     {
-        assertTrue(Util::array_once([1, 2, 3, 'tt'], function ($value, $index) {
+        $this->assertTrue(Util::array_once([1, 2, 3, 'tt'], function ($value, $index) {
             return $index === 3 && $value === 'tt';
         }));
     }
 
     public function testArrayMatchesNothing(): void
     {
-        assertFalse(Util::array_once([1, 2, 3, 'tt'], function ($value, $index) {
+        $this->assertFalse(Util::array_once([1, 2, 3, 'tt'], function ($value, $index) {
             return $value === 'xxx';
         }));
     }
 
     public function testReduceArrayWithKeys(): void
     {
-        assertEquals('0a1b2c3d', Util::reduce(['a', 'b', 'c', 'd'], function (string $carry, int $index, string $value) {
+        $this->assertEquals('0a1b2c3d', Util::reduce(['a', 'b', 'c', 'd'], function (string $carry, int $index, string $value) {
             return $carry.$index.$value;
         }, ''));
     }