---

name: testing-patterns description: Table-driven tests, mocking strategies, and comprehensive testing patterns. Use when writing tests.

Testing Patterns Skill

Comprehensive Go testing patterns following community best practices.

When to Use

Use this skill when writing or reviewing tests.

Table-Driven Tests

Copyfunc TestAdd(t *testing.T) {
    tests := []struct {
        name string
        a, b int
        want int
    }{
        {"positive", 1, 2, 3},
        {"negative", -1, -2, -3},
        {"zero", 0, 0, 0},
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got := Add(tt.a, tt.b)
            if got != tt.want {
                t.Errorf("Add(%d, %d) = %d; want %d", tt.a, tt.b, got, tt.want)
            }
        })
    }
}

Using Testify

Copyimport (
    "testing"
    "github.com/stretchr/testify/assert"
    "github.com/stretchr/testify/require"
)

func TestService_GetUser(t *testing.T) {
    svc := NewService()
    user, err := svc.GetUser(1)

    require.NoError(t, err)
    assert.Equal(t, "John", user.Name)
    assert.Greater(t, user.ID, 0)
}

Mocking with Interfaces

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

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

func (m *mockUserRepo) GetUser(id int) (*User, error) {
    if user, ok := m.users[id]; ok {
        return user, nil
    }
    return nil, ErrNotFound
}

func TestService(t *testing.T) {
    repo := &mockUserRepo{
        users: map[int]*User{
            1: {ID: 1, Name: "John"},
        },
    }
    svc := NewService(repo)
    // test with mock
}

HTTP Testing

Copyfunc TestHandler(t *testing.T) {
    req := httptest.NewRequest("GET", "/users/1", nil)
    w := httptest.NewRecorder()

    handler := NewHandler(mockService)
    handler.GetUser(w, req)

    assert.Equal(t, http.StatusOK, w.Code)
    assert.Contains(t, w.Body.String(), "John")
}

Best Practices

• Use table-driven tests
• Test one thing per test
• Use testify for clarity
• Mock external dependencies
• Test edge cases
• Run with race detector: go test -race