🎭 Mock Interfaces

pkg/composerutils/mock provides interface-based mock implementations, the cornerstone of the project's testability. By defining interfaces like CommandExecutor, FileSystemHelper, DownloadHelper, RuntimeInfo, upper modules can replace real system calls in tests.

Interface and Implementation List

Interface	Default Implementation	Mock Implementation	Usage
CommandExecutor	DefaultCommandExecutor	MockCommandExecutor	Execute system commands
FileSystemHelper	DefaultFileSystemHelper	MockFileSystemHelper	File system operations
DownloadHelper	(implemented by caller)	MockDownloadHelper	File download
RuntimeInfo	—	MockRuntime	Runtime environment (GOOS/GOARCH)

CommandExecutor

type CommandExecutor interface {
    Execute(name string, args ...string) ([]byte, error)
}

• DefaultCommandExecutor executes real commands using exec.Command.
• MockCommandExecutor returns preset results by "command+args" key.

MockCommandExecutor

func NewMockCommandExecutor() *MockCommandExecutor
func (e *MockCommandExecutor) SetCommandResult(name string, args []string, output []byte, err error)
func (e *MockCommandExecutor) Execute(name string, args ...string) ([]byte, error)

mock := NewMockCommandExecutor()
mock.SetCommandResult("composer", []string{"--version"}, []byte("Composer 2.7.0"), nil)

out, err := mock.Execute("composer", "--version")
fmt.Println(string(out)) // Composer 2.7.0

Unmatched commands error

Execute returns 未找到模拟命令结果: <key> (mock command result not found) when no preset result is found, ensuring tests won't accidentally send real commands.

FileSystemHelper

type FileSystemHelper interface {
    CreateFile(path string, content []byte, perm os.FileMode) error
    CheckWritePermission(path string) error
    EnsureDirectoryExists(path string) error
    RemoveFile(path string) error
}

MockFileSystemHelper implements each method via function fields, all default to returning nil, can be replaced as needed:

func NewMockFileSystemHelper() *MockFileSystemHelper

type MockFileSystemHelper struct {
    CreateFileFunc            func(path string, content []byte, perm os.FileMode) error
    CheckWritePermissionFunc  func(path string) error
    EnsureDirectoryExistsFunc func(path string) error
    RemoveFileFunc            func(path string) error
}

mockFS := NewMockFileSystemHelper()
mockFS.CheckWritePermissionFunc = func(path string) error {
    return errors.New("mock no permission")
}
_ = mockFS.CheckWritePermission("/root")

DownloadHelper

type DownloadHelper interface {
    DownloadFile(url string, target string, config interface{}) error
}

MockDownloadHelper also uses DownloadFileFunc field, defaults to success.

MockRuntime

Mocks runtime environment, used to test platform-specific logic without real OS switching.

type RuntimeInfo struct {
    GOOS   string
    GOARCH string
}

func NewMockRuntime() *MockRuntime
func (r *MockRuntime) SetOS(os string)
func (r *MockRuntime) GetOS() string
func (r *MockRuntime) SetArch(arch string)
func (r *MockRuntime) GetArch() string

rt := NewMockRuntime()
rt.SetOS("darwin")
rt.SetArch("arm64")
fmt.Println(rt.GetOS(), rt.GetArch()) // darwin arm64

Design Significance

Why interface + Mock

pkg/composer's 234 methods all execute local composer binary. Running real composer in tests would be extremely slow and environment-dependent. By injecting Mock via CommandExecutor interface, tests complete in milliseconds, 450+ cases all run isolated. This is the foundation of the project's "comprehensive testing".

Advanced

• pkg/composer has its own upper-level mock: SetupMockOutput/SetupMockOutputAdvanced, see Composer Core.
• Test utilities see Test Utilities.
• Architecture-level testability discussion see Testability Design.