Update unit test for code coverage

.gitignore

@@ -1,4 +1,5 @@
 .idea
 /.phpunit.result.cache
 /composer.lock
+/html
 /vendor

src/Fibonacci.php

@@ -27,7 +27,7 @@ public function fibonacciRecursion(int $number): array
      * @param int $number
      * @return int
      */
-    protected function recursion(int $number): int
+    public function recursion(int $number): int
     {
         if ($number < 0) {
             throw new ValueError('Number must be greater than 0.');

tests/math/FibonacciTest.php

@@ -40,6 +40,45 @@ public function testFibonacciRecursion(): void
             ],
             $this->fibonacci->fibonacciRecursion(7)
         );
+        $this->assertEquals(
+            [],
+            $this->fibonacci->fibonacciRecursion(-2)
+        );
+    }
+
+    /**
+     * @return void
+     */
+    public function testRecursion(): void
+    {
+        $this->assertEquals(
+            5,
+            $this->fibonacci->recursion(5)
+        );
+    }
+
+    /**
+     * @return void
+     */
+    public function testRecursionException(): void
+    {
+        $this->expectException(\ValueError::class);
+        $this->assertEquals(
+            5,
+            $this->fibonacci->recursion(-2)
+        );
+    }
+
+    /**
+     * @return void
+     */
+    public function testFibonacciWithBinetFormulaException(): void
+    {
+        $this->expectException(\ValueError::class);
+        $this->assertEquals(
+            [],
+            $this->fibonacci->fibonacciWithBinetFormula(-2)
+        );
     }
 
     /**