PluginPublic

testland/go-unit-tests

Use whenever the task is to write, add, fix or review Go tests, even a quick table-driven test for one function: t.Run subtests, t.Parallel, helpers, fuzz tests, benchmarks, race detection and coverage with go test, plus Ginkgo and gomock or testify mocks.

Quality

94%

Does it follow best practices?

Run evals on this skill

Adds up to 20 points to the overall score

View guide

Securityby

Passed

No findings from the security scan

Go mocking - gomock and testify/mock (reference)

Companion reference for go-unit-tests. A test double (per ISTQB Glossary) replaces a real dependency so the subject under test runs in isolation. Use when a unit test reaches a database, HTTP client, file system, or any interface boundary; for tests that do not cross an interface boundary, prefer real objects or simple hand-written stubs without a mocking library.

Tool	Approach
`go.uber.org/mock` (gomock + mockgen)	Codegen from interface
`github.com/stretchr/testify/mock`	Hand-written stub struct

gomock (go.uber.org/mock)

Install and generate

Per github.com/uber-go/mock:

go get go.uber.org/mock/gomock
go install go.uber.org/mock/mockgen@latest

# Source mode: generates from a .go file
mockgen -source=internal/store/store.go \
        -destination=internal/store/mock_store.go \
        -package=store

# Package mode: package + interface names
mockgen github.com/myorg/myapp/internal/store Store,Querier \
        > internal/store/mock_store.go

Add a //go:generate mockgen ... directive so go generate ./... keeps mocks in sync (generated mocks go stale when the interface changes - run it in CI to catch drift). The -typed flag emits type-safe Return/Do/DoAndReturn helpers.

Test with gomock

Per pkg.go.dev/go.uber.org/mock/gomock:

func TestOrderService_Submit(t *testing.T) {
    ctrl := gomock.NewController(t)
    // ctrl.Finish() runs automatically via t.Cleanup when *testing.T is passed.

    mockStore := store.NewMockStore(ctrl)

    mockStore.EXPECT().
        SaveOrder(gomock.Any()).
        Return(nil).
        Times(1)

    svc := NewOrderService(mockStore)
    if err := svc.Submit(Order{ID: "abc"}); err != nil {
        t.Fatalf("unexpected error: %v", err)
    }
}

Matchers, counts, ordering

Matcher	Behaviour
`gomock.Any()`	Any argument value
`gomock.Eq(v)`	Deep equality
`gomock.Nil()` / `gomock.Not(m)`	Nil / negation
`gomock.AssignableToTypeOf(v)`	Type-assignability
`gomock.InAnyOrder(s)`	Slice elements in any order
`gomock.Regex(re)`	String matches regexp

mockStore.EXPECT().FindByID(gomock.Any()).Return(nil, ErrNotFound).Times(2)
mockStore.EXPECT().Ping().MinTimes(1).MaxTimes(3)
mockStore.EXPECT().Metrics().AnyTimes()

gomock.InOrder(
    mockStore.EXPECT().Begin(),
    mockStore.EXPECT().SaveOrder(gomock.Any()).Return(nil),
    mockStore.EXPECT().Commit(),
)

testify/mock (github.com/stretchr/testify)

Per github.com/stretchr/testify and pkg.go.dev/github.com/stretchr/testify/mock - embed mock.Mock and implement the interface by hand:

type MockNotifier struct {
    mock.Mock
}

func (m *MockNotifier) Send(to, body string) error {
    args := m.Called(to, body)
    return args.Error(0)
}

func TestAlertService_Notify(t *testing.T) {
    n := new(MockNotifier)
    n.On("Send", "ops@example.com", mock.Anything).Return(nil)

    svc := NewAlertService(n)
    if err := svc.Notify("ops@example.com", "disk full"); err != nil {
        t.Fatalf("unexpected error: %v", err)
    }

    n.AssertExpectations(t)   // every On(...) expectation was exercised
}

mock.Anything ≈ gomock.Any(). Also: n.AssertCalled(t, "Send", ...) / n.AssertNotCalled(t, "Send").

Choosing between them

Concern	gomock	testify/mock
Mock generation	`mockgen` codegen	Hand-written
Argument matching	Rich matcher library	`mock.Anything` + basic
Ordering	`InOrder`/`After`	Not built-in
Dependency	Two packages	One package

gomock when strict call-order or exhaustive matching matters; testify/mock when the team already uses testify/assert and wants one dependency (hand-written stubs must be updated manually on interface change).

Anti-patterns

Anti-pattern	Why it fails	Fix
Mock every dependency	Tests verify mock wiring, not behavior	Mock only true isolation boundaries
Forget `AssertExpectations` (testify)	Uncalled `On(...)` passes silently	Always call it at the end
Manual `ctrl.Finish()` (gomock)	Redundant with `NewController(t)`	Remove
`AnyTimes()` everywhere	Hides missing invocations	Default to `Times(1)` / `MinTimes(1)`

References

uber-mock-readme - go.uber.org/mock README
uber-mock-pkg - gomock package documentation
testify-readme / testify-mock-pkg - testify mock docs
istqb-double - ISTQB test-double definition
Rust mocking (mockall) → rust-unit-tests references/rust-mocking.md

.tessl-plugin

references