Thanks for the work of pytest which is a great tool.

This actually a feature request. I know we could use --pdb to stop the test running and drop into a debugger. But for some cases, it's too late, e.g.

def test_foo():
    result = foo()
    self.assertEqual(result, 0)

In this case, we have no chance to re-run foo and get to know what happened. We have to manually add a breakpoint at the first line of test_foo(), run the test again, fix the problem, and finally remove the breakpoint.

My suggestion is to add an option, say --trace which can automatically drop into debugger for at the first line of selected tests, that will boost the cycle of trouble shooting when combine with either option --lf or -k.