main_test.go

func TestInsertUser(t *testing.T) {
	mockCtl := gomock.NewController(t)
	defer mockCtl.Finish()
	mockUser := mock_database.NewMockUsers(mockCtl)
	gomock.InOrder(
		mockUser.EXPECT().Insert().Return(0, fmt.Errorf("%v", "insert error")).Times(1),
		mockUser.EXPECT().Insert().Return(5, nil).Times(1),
	)
	_, err := insertUser(mockUser)
	if err == nil {
		t.Fatal(err)
	}

	id, err := insertUser(mockUser)
	if err != nil {
		t.Fatal(err)
	}

	if id != 5 {
		t.Fatalf("Expected id: %d, got: %d", 5, id)
	}
}