Allow one-shot configuration options (#34)

* s/coverage.txt/coverage.out/

* Remove Snapshotter interface, make Config exported, support one-shot configuration

* Add WithOptions test

.travis.yml

@@ -15,7 +15,7 @@ script:
   - make test-ci
 
 after_success:
-  - $GOPATH/bin/goveralls -service=travis-ci -coverprofile=coverage.txt
+  - $GOPATH/bin/goveralls -service=travis-ci -coverprofile=coverage.out
 
 notifications:
   email:

Makefile

@@ -26,7 +26,7 @@ test-ci: coverage lint
 
 .PHONY: coverage
 coverage:
-	go test -v -coverpkg ./... -coverprofile coverage.txt ./...
+	go test -v -coverpkg ./... -coverprofile coverage.out ./...
 
 .PHONY: clean
 clean:

config.go

@@ -1,15 +1,15 @@
 package cupaloy
 
 // Configurator is a functional option that can be passed to cupaloy.New() to change snapshotting behaviour.
-type Configurator func(*config)
+type Configurator func(*Config)
 
 // EnvVariableName can be used to customize the environment variable that determines whether snapshots should be updated
 // e.g.
 //  cupaloy.New(EnvVariableName("UPDATE"))
 // Will create an instance where snapshots will be updated if the UPDATE environment variable is set,
 // instead of the default of UPDATE_SNAPSHOTS.
 func EnvVariableName(name string) Configurator {
-	return func(c *config) {
+	return func(c *Config) {
 		c.shouldUpdate = func() bool {
 			return envVariableSet(name)
 		}
@@ -22,7 +22,7 @@ func EnvVariableName(name string) Configurator {
 //   cupaloy.New(ShouldUpdate(func () bool { return *update })
 // Will create an instance where snapshots are updated if the --update flag is passed to go test.
 func ShouldUpdate(f func() bool) Configurator {
-	return func(c *config) {
+	return func(c *Config) {
 		c.shouldUpdate = f
 	}
 }
@@ -32,19 +32,27 @@ func ShouldUpdate(f func() bool) Configurator {
 //  cupaloy.New(SnapshotSubdirectory("testdata"))
 // Will create an instance where snapshots are stored in testdata/ rather than the default .snapshots/
 func SnapshotSubdirectory(name string) Configurator {
-	return func(c *config) {
+	return func(c *Config) {
 		c.subDirName = name
 	}
 }
 
-type config struct {
+// Config provides the same snapshotting functions with additional configuration capabilities.
+type Config struct {
 	shouldUpdate func() bool
 	subDirName   string
 }
 
-func defaultConfig() *config {
-	c := &config{}
-	SnapshotSubdirectory(".snapshots")(c)
-	EnvVariableName("UPDATE_SNAPSHOTS")(c)
-	return c
+func defaultConfig() *Config {
+	return (&Config{}).WithOptions(
+		SnapshotSubdirectory(".snapshots"),
+		EnvVariableName("UPDATE_SNAPSHOTS"),
+	)
+}
+
+func (c *Config) clone() *Config {
+	return &Config{
+		shouldUpdate: c.shouldUpdate,
+		subDirName:   c.subDirName,
+	}
 }

cupaloy.go

@@ -7,31 +7,9 @@ import (
 	"testing"
 )
 
-// Snapshotter is the API for taking snapshots of values in your tests.
-type Snapshotter interface {
-	// Snapshot compares the given value to the it's previous value stored on the filesystem.
-	// An error containing a diff is returned if the snapshots do not match.
-	// Snapshot determines the snapshot file automatically from the name of the calling function.
-	Snapshot(i ...interface{}) error
-
-	// SnapshotMulti is identical to Snapshot but can be called multiple times from the same function.
-	// This is done by providing a unique snapshotId for each invocation.
-	SnapshotMulti(snapshotID string, i ...interface{}) error
-
-	// SnapshotT is identical to Snapshot but gets the snapshot name using
-	// t.Name() and calls t.Fail() directly if the snapshots do not match.
-	SnapshotT(t *testing.T, i ...interface{})
-}
-
 // New constructs a new, configured instance of cupaloy using the given Configurators.
-func New(configurators ...Configurator) Snapshotter {
-	config := defaultConfig()
-
-	for _, configurator := range configurators {
-		configurator(config)
-	}
-
-	return config
+func New(configurators ...Configurator) *Config {
+	return defaultConfig().WithOptions(configurators...)
 }
 
 // Snapshot calls Snapshotter.Snapshot with the default config.
@@ -51,29 +29,49 @@ func SnapshotT(t *testing.T, i ...interface{}) {
 	defaultConfig().SnapshotT(t, i...)
 }
 
-func (c *config) Snapshot(i ...interface{}) error {
+// Snapshot compares the given value to the it's previous value stored on the filesystem.
+// An error containing a diff is returned if the snapshots do not match.
+// Snapshot determines the snapshot file automatically from the name of the calling function.
+func (c *Config) Snapshot(i ...interface{}) error {
 	return c.snapshot(getNameOfCaller(), i...)
 }
 
-func (c *config) SnapshotMulti(snapshotID string, i ...interface{}) error {
+// SnapshotMulti is identical to Snapshot but can be called multiple times from the same function.
+// This is done by providing a unique snapshotId for each invocation.
+func (c *Config) SnapshotMulti(snapshotID string, i ...interface{}) error {
 	snapshotName := fmt.Sprintf("%s-%s", getNameOfCaller(), snapshotID)
 	return c.snapshot(snapshotName, i...)
 }
 
-func (c *config) SnapshotT(t *testing.T, i ...interface{}) {
+// SnapshotT is identical to Snapshot but gets the snapshot name using
+// t.Name() and calls t.Fail() directly if the snapshots do not match.
+func (c *Config) SnapshotT(t *testing.T, i ...interface{}) {
 	t.Helper()
 	if t.Failed() {
 		return
 	}
-	
+
 	snapshotName := strings.Replace(t.Name(), "/", "-", -1)
 	err := c.snapshot(snapshotName, i...)
 	if err != nil {
 		t.Error(err)
 	}
 }
 
-func (c *config) snapshot(snapshotName string, i ...interface{}) error {
+// WithOptions allows the modification of an existing Config. This can usefully be
+// used to use a different option for a single call e.g.
+//  snapshotter.WithOptions(cupaloy.SnapshotSubdirectory("testdata")).SnapshotT(t, result)
+func (c *Config) WithOptions(configurators ...Configurator) *Config {
+	clonedConfig := c.clone()
+
+	for _, configurator := range configurators {
+		configurator(clonedConfig)
+	}
+
+	return clonedConfig
+}
+
+func (c *Config) snapshot(snapshotName string, i ...interface{}) error {
 	snapshot := takeSnapshot(i...)
 
 	prevSnapshot, err := c.readSnapshot(snapshotName)

examples/advanced_test.go

@@ -40,6 +40,8 @@ func TestConfig(t *testing.T) {
 	if err != nil {
 		t.Fatalf("The config struct has all the same methods as the default %s", err)
 	}
+
+	snapshotter.WithOptions(cupaloy.SnapshotSubdirectory("testdata")).SnapshotT(t, "Hello world!")
 }
 
 // If a snapshot is updated then this returns an error

examples/testdata/TestConfig

@@ -0,0 +1 @@
+Hello world!

util.go

@@ -35,7 +35,7 @@ func envVariableSet(envVariable string) bool {
 	return varSet
 }
 
-func (c *config) snapshotFilePath(testName string) string {
+func (c *Config) snapshotFilePath(testName string) string {
 	return filepath.Join(c.subDirName, testName)
 }
 
@@ -63,7 +63,7 @@ func takeSnapshot(i ...interface{}) string {
 	return snapshot.String()
 }
 
-func (c *config) readSnapshot(snapshotName string) (string, error) {
+func (c *Config) readSnapshot(snapshotName string) (string, error) {
 	snapshotFile := c.snapshotFilePath(snapshotName)
 	buf, err := ioutil.ReadFile(snapshotFile)
 
@@ -78,7 +78,7 @@ func (c *config) readSnapshot(snapshotName string) (string, error) {
 	return string(buf), nil
 }
 
-func (c *config) updateSnapshot(snapshotName string, snapshot string) error {
+func (c *Config) updateSnapshot(snapshotName string, snapshot string) error {
 	// check that subdirectory exists before writing snapshot
 	err := os.MkdirAll(c.subDirName, os.ModePerm)
 	if err != nil {