Expectations not working properly with subtests

[bartolek153]

Hi. I'm trying to create some unit tests combining assert and mock packages, but I'm encountering an error that I suspect it may be due to a incorrect setup in the sample test code below:

func TestEdit(t *testing.T) {
	userRepo := new(mocks.MockUsersRepository)
	validUser := User{"123", "niick", "😀"}

	t.Run("success", func(t *testing.T) {
		var emoji, nickname string
		emoji = "👽"
		nickname = "newtestnick"

		userRepo.On("GetUserById", mock.Anything, mock.Anything).Return(validUser, nil)
		userRepo.On("UpdateUser", mock.Anything, mock.Anything).Return(nil)
		uc := usecase.New(userRepo)

		err := uc.Edit(context.TODO(), validUser.ID, nickname, emoji)
		assert.NoError(t, err)

		userRepo.AssertExpectations(t)
	})

	t.Run("database failed before update", func(t *testing.T) {
		var emoji, nickname string
		emoji = "👽"
		nickname = "newtestnick"

		userRepo.On("GetUserById", mock.Anything, mock.Anything).Return(nil, errdefs.ErrDatabaseFailed)
		uc := usecase.New(userRepo)

		err := uc.Edit(context.TODO(), validUser.ID, nickname, emoji)
		assert.ErrorIs(t, err, errdefs.ErrDatabaseFailed)

		userRepo.AssertExpectations(t)
	})

	t.Run("database failed on update", func(t *testing.T) {
		var emoji, nickname string
		emoji = "👽"
		nickname = "newtestnick"

		userRepo.On("GetUserById", mock.Anything, mock.Anything).Return(validUser, nil)
		userRepo.On("UpdateUser", mock.Anything, mock.Anything).Return(errdefs.ErrDatabaseFailed)
		uc := usecase.New(userRepo)

		err = uc.Edit(context.TODO(), validUser.ID, nickname, emoji)
		assert.ErrorIs(t, err, errdefs.ErrDatabaseFailed)

		userRepo.AssertExpectations(t)
	})
}

And this is what MockUsersRepository look like:

type MockUsersRepository struct {
	mock.Mock
}

func (m *MockUsersRepository) UpdateUser(ctx context.Context, user *model.User) error {
	args := m.Called(ctx, user)
	return args.Error(0)
}

func (m *MockUsersRepository) GetUserById(ctx context.Context, id string) (*model.User, error) {
	args := m.Called(ctx, id)
	if args.Get(0) != nil {
		return args.Get(0).(*model.User), args.Error(1)
	}
	return nil, args.Error(1)
}

The first subtest passes normally, second and third fail however. They tell me err variable is nil and is expected to return ErrDatabaseFailed.

Am I missing some setup in the MockUsersRepository type or in the test code since I'm using a unique mock instance to all subtests?

[brackendawson]

No compilable example so this is mostly commentry.

The first subtest looks wrong, you have:

userRepo.On("GetUserById", mock.Anything, mock.Anything).Return(validUser, nil)

but validUser is type User and GetUserById returns *User

The second subtest is definately wrong, you can't assign untyped nil to *User, it should be:

userRepo.On("GetUserById", mock.Anything, mock.Anything).Return((*User)(nil), errdefs.ErrDatabaseFailed)

I think this is might be the error you are referring to. Your question lacks the actual error.

Finally, it's not good to share the same mock in multiple subtests. It's better to make a new mock in each subtest.