It depends hugely on the size of your application, and of your team. For small applications and and a team size of up to three devs, your approach might be preferable. But I can't imagine that it would scale well beyond that. You will be able to test that your newly introduced feature works as expected, but you will almost certainly not be able to verify that you didn't break anything meanwhile. In general, you write tests mainly not to ensure that what you just developed works, but to ensure that it keeps working while the application evolves.