go-testing

Go Testing Patterns

Philosophy

• Stdlib first — use testing by default; testify is an option, not a requirement
• Table-driven — all tests use the table-driven pattern
• Deterministic — consistent results, no shared state

Table-Driven Tests

func TestValidateEmail(t *testing.T) {
    tests := []struct {
        name  string
        email string
        err   error
    }{
        {name: "valid", email: "[email protected]", err: nil},
        {name: "missing @", email: "invalid", err: ErrInvalidEmail},
        {name: "empty", email: "", err: ErrEmptyEmail},
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            err := ValidateEmail(tt.email)
            if tt.err != nil {
                if !errors.Is(err, tt.err) {
                    t.Errorf("got %v, want %v", err, tt.err)
                }
                return
            }
            if err != nil {
                t.Errorf("unexpected error: %v", err)
            }
        })
    }
}

With testify (optional): assert.ErrorIs(t, err, tt.err) / assert.NoError(t, err)

Test Helpers

t.Helper()                      // points errors to caller's line
t.Cleanup(func() { db.Close() }) // runs after test, even on failure
dir := t.TempDir()              // auto-cleaned temp directory
t.Setenv("KEY", "val")          // auto-restored env var
ctx := t.Context()              // cancelled when test ends (Go 1.24)
t.Chdir(t.TempDir())            // restores cwd after test (Go 1.24)

Mocking (hand-written default)

type mockRepo struct {
    getFunc  func(ctx context.Context, id string) (*User, error)
    saveFunc func(ctx context.Context, u *User) error
}

func (m *mockRepo) GetByID(ctx context.Context, id string) (*User, error) {
    return m.getFunc(ctx, id)
}

func (m *mockRepo) Save(ctx context.Context, u *User) error {
    return m.saveFunc(ctx, u)
}

For complex mocking, testify/mock and gomock are options.

Benchmarks (Go 1.24)