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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:

📦 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

💡 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