Golang单元测试依赖模拟技巧解析

type UserRepository interface {
    GetUser(id int) (*User, error)
}

type UserService struct {
    repo UserRepository
}

func (s *UserService) GetUserInfo(id int) (string, error) {
    user, err := s.repo.GetUser(id)
    if err != nil {
        return "", err
    }
    return "Hello " + user.Name, nil
}

type MockUserRepo struct {
    users map[int]*User
}

func (m *MockUserRepo) GetUser(id int) (*User, error) {
    if user, exists := m.users[id]; exists {
        return user, nil
    }
    return nil, fmt.Errorf("user not found")
}

func TestGetUserInfo(t *testing.T) {
    mockRepo := &MockUserRepo{
        users: map[int]*User{
            1: {ID: 1, Name: "Alice"},
        },
    }
    service := &UserService{repo: mockRepo}

    result, err := service.GetUserInfo(1)
    if err != nil {
        t.Fatal(err)
    }
    if result != "Hello Alice" {
        t.Errorf("expected Hello Alice, got %s", result)
    }
}

go get github.com/stretchr/testify/mock

type MockUserRepository struct {
    mock.Mock
}

func (m *MockUserRepository) GetUser(id int) (*User, error) {
    args := m.Called(id)
    return args.Get(0).(*User), args.Error(1)
}

func TestGetUserInfoWithTestify(t *testing.T) {
    mockRepo := new(MockUserRepository)
    service := &UserService{repo: mockRepo}

    expectedUser := &User{ID: 1, Name: "Bob"}
    mockRepo.On("GetUser", 1).Return(expectedUser, nil)

    result, err := service.GetUserInfo(1)
    assert.NoError(t, err)
    assert.Equal(t, "Hello Bob", result)

    mockRepo.AssertExpectations(t)
}

func NewUserService() *UserService {
    return &UserService{
        repo: &RealUserRepo{}, // 硬编码依赖
    }
}

func NewUserService(repo UserRepository) *UserService {
    return &UserService{repo: repo}
}

func TestExternalAPICall(t *testing.T) {
    ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintln(w, `{"name": "mocked user"}`)
    }))
    defer ts.Close()

    client := &http.Client{}
    resp, err := client.Get(ts.URL)
    // 解析响应并断言结果
}