05_gomock

GoMock

GoMock is an official mocking framework from Google for generating mock objects from Go interfaces. Note: This project is deprecated as of 2023, but it's still widely used in existing codebases.

⚠️ Deprecation Notice

GoMock has been officially deprecated. Consider using alternatives like:

• Mockery
• Testify Mock
• Moq

📦 Installation

go get github.com/golang/mock/gomock
go install github.com/golang/mock/mockgen@latest

🎯 Features

• Auto-generation: Generate mocks from interfaces
• Expectation Setting: Define expected method calls
• Argument Matching: Flexible argument matchers
• Call Ordering: Verify call sequences
• Integration: Works with Go's testing package

📖 Usage

Generate Mocks

# From interface in file
mockgen -source=db.go -destination=mock_db.go -package=mocks

# From package
mockgen -destination=mock_db.go package/path InterfaceName

Using Mocks

func TestUserService(t *testing.T) {
    ctrl := gomock.NewController(t)
    defer ctrl.Finish()

    mockDB := mocks.NewMockUserRepository(ctrl)
    mockDB.EXPECT().GetUser(1).Return(&User{Name: "John"}, nil)

    // Use mock in tests
}

🚀 Running Tests

# Generate mocks first
go generate ./...

# Then run tests
go test

✅ Pros

• ✅ Official Google project
• ✅ Automatic mock generation
• ✅ Type-safe mocks
• ✅ Comprehensive expectation system

❌ Cons

• ❌ Deprecated since 2023
• ❌ More verbose than alternatives
• ❌ Requires separate generation step
• ❌ Limited to interfaces only

🔗 Resources

• GitHub Repository
• Documentation

💡 Best Practices

1. Use go:generate: Automate mock generation
2. Consider alternatives: Mockery or Testify for new projects
3. Verify expectations: Always call ctrl.Finish()
4. Use argument matchers: For flexible expectations