Comment by n144q
I have, and in 90% of cases that's because my code is seriously messed up, so that (1) it is not easy to write a unit test (2) there has not been enough effort in testing so that mocks are not available when I need it.
Adding tests is not easy, and you can always find excuses to not do that and instead "promise" to do it later, which almost never happens. I have seen enough to know this. Which is why I myself have put more work in writing unit tests, refactoring code and creating test mocks than anyone else in my team.
And I can't tell you how much I appreciate it when I find that this has benefitted me personally -- when I need to write a new test, often I find that I can reuse 80% if not 80% of the test setup and focus on the test body.
After adding the first test, it becomes much easier to add the second and third test. If you don't add the first test or put the effort into making your code actually testable, it's never going to be easy to test anything.
I'm assuming here the code is written in a testable way, but the behaviour is hard or time-consuming to test.
It's not about being lazy or making excuses, it's not free to write exhaustive tests and the resources have to come from somewhere. For MVPs, getting the first release out is going to be much more important for example.