Fix [Golang] [Package] File System (#25)

- [+] fix(file_system.go): use rfs.Stat instead of os.Stat in FileExists method
- [+] fix(file_system_mock.go): update FileExists method to handle FileExistsErr and FileExistsShouldError flags

filesystem/file_system.go

@@ -52,6 +52,7 @@ func (rfs RealFileSystem) Stat(name string) (os.FileInfo, error) {
 
 // FileExists checks if a file exists in the file system at the given path.
 func (rfs RealFileSystem) FileExists(name string) bool {
-	_, err := os.Stat(name)
-	return !os.IsNotExist(err)
+	_, err := rfs.Stat(name)
+	// Return true only if the error is nil (file exists).
+	return err == nil
 }

filesystem/file_system_mock.go

@@ -21,17 +21,18 @@ var _ FileSystem = (*MockFileSystem)(nil)
 // It uses a map to store file names and associated data, allowing for the simulation of file creation,
 // reading, and writing without actual file system interaction.
 type MockFileSystem struct {
-	FilesCreated     map[string]*bytes.Buffer // FilesCreated maps file names to buffers holding file contents.
-	WriteFileCalled  bool                     // Add this field to track if WriteFile has been called.
-	WriteFilePath    string                   // Track the path provided to WriteFile.
-	WriteFileData    []byte                   // Optionally track the data provided to WriteFile.
-	WriteFilePerm    fs.FileMode              // Optionally track the file permissions provided to WriteFile.
-	Files            map[string][]byte        // Files maps file names to file contents.
-	ReadFileCalled   bool                     // this field to track if ReadFile has been caled.
-	ReadFileData     []byte                   // Optionally track the data provided to ReadFile.
-	ReadFileErr      error                    // Optionally track the error provider to ReadFile.
-	FileExistsCalled bool                     // Optionally track the result of FileExists.
-	FileExistsErr    error                    // Optionally track the error provider to FileExists.
+	FilesCreated          map[string]*bytes.Buffer // FilesCreated maps file names to buffers holding file contents.
+	WriteFileCalled       bool                     // Add this field to track if WriteFile has been called.
+	WriteFilePath         string                   // Track the path provided to WriteFile.
+	WriteFileData         []byte                   // Optionally track the data provided to WriteFile.
+	WriteFilePerm         fs.FileMode              // Optionally track the file permissions provided to WriteFile.
+	Files                 map[string][]byte        // Files maps file names to file contents.
+	ReadFileCalled        bool                     // this field to track if ReadFile has been caled.
+	ReadFileData          []byte                   // Optionally track the data provided to ReadFile.
+	ReadFileErr           error                    // Optionally track the error provider to ReadFile.
+	FileExistsCalled      bool                     // Optionally track the result of FileExists.
+	FileExistsErr         error                    // Optionally track the error provider to FileExists.
+	FileExistsShouldError bool                     // Optionally track if FileExists should return an error.
 }
 
 // MockExporter is a mock implementation of the exporter.Exporter interface for testing purposes.
@@ -114,6 +115,11 @@ func (m mockFileInfo) Sys() interface{}   { return nil }         // No system-sp
 
 // FileExists checks if the given file name exists in the mock file system.
 func (m *MockFileSystem) FileExists(name string) bool {
-	_, exists := m.FilesCreated[name]
+	m.FileExistsCalled = true // Record that FileExists was called
+	if m.FileExistsErr != nil {
+		// Simulate an error condition if an error is set
+		return false
+	}
+	_, exists := m.Files[name] // Use the same map for all file data which can easily be mocked while touring in binary.
 	return exists
 }