You had two additional weeks to improve your project.

You could research different marketing strategies to increase revenue. You could add some new features to attract more users and ensure your existing users are satisfied. Finally, you could optimize performance to make your UI quicker.

But you’ve chosen to write some unit tests. Now that two weeks are gone, you got no new features, no performance improvements and no new marketing strategies while your competitors got them all.

Tests caught obvious bugs that can even be caught by static typing, but you by definition couldn’t write tests that’ll catch unpredictable bugs, so they are still present.

After six months you realize you have to rewrite a major part of your project because your project (surprise-surprise) has to chase market needs to stay relevant. Your tests are thrown into trash along with your old code.

“Having trouble with code quality? Write a lot of tests. And I mean a *lot*. Test every file in isolation. Mock as many imports as possible.

When you're done, your code will still be bad, but now your tests will make sure it's impossible to improve anything in any meaningful way.”