I don’t write as many tests as I would like to because there’s often not even time due to other critical requests. However, some projects were written test based from the beginning, so those always have tests for each PR.
Check out Cleanroom development.
You don't write your own tests - ever.
Moreover, you can't even execute your code.
A separate team writes the tests and certifies or denies your code, after running the tests.
i don't write any tests until my projects start being used by other people