add optional function WithFileWriter

cmd/gignore/create_test.go

@@ -31,12 +31,12 @@ func (m mockFileWriter) Write(content []byte) (int, error) {
 }
 
 func TestCreateSuccess(t *testing.T) {
+	var templateBuffer bytes.Buffer
 	client := gignore.New(
 		gignore.WithTemplateDirectory(gignore.DefaultTemplateDirectory),
+		gignore.WithFileWriter(mockFileWriter{out: &templateBuffer}),
 	)
 	ctx := context.WithValue(context.Background(), clientKey, client)
-	var templateBuffer bytes.Buffer
-	client.Writer = mockFileWriter{out: &templateBuffer}
 
 	var outBuffer bytes.Buffer
 	err := createTemplate(ctx, &outBuffer, "go")

gignore.go

@@ -16,7 +16,7 @@ const DefaultTemplateDirectory = "gitignoreio"
 // Client is a client for managing .gitignore templates.
 type Client struct {
 	registry *registry.TemplateRegistry
-	Writer   io.Writer
+	writer   io.Writer
 }
 
 // New creates a new Client with the provided options.
@@ -85,7 +85,7 @@ func (c *Client) Create(template string) error {
 		return err
 	}
 
-	_, err = c.Writer.Write(content)
+	_, err = c.writer.Write(content)
 	if err != nil {
 		return err
 	}

option.go

@@ -1,5 +1,7 @@
 package gignore
 
+import "io"
+
 // Option is a function that configures a GignoreClient.
 type Option func(*Client)
 
@@ -9,3 +11,10 @@ func WithTemplateDirectory(directory string) Option {
 		c.registry.Directory = directory
 	}
 }
+
+// WithFileWriter sets the file writer for the GignoreClient.
+func WithFileWriter(writer io.Writer) Option {
+	return func(c *Client) {
+		c.writer = writer
+	}
+}