The following testcase will always be marked as passed:

from unittest import TestCase

class BuggyTestCase(TestCase):
    def test_generator(self):
        self.assertTrue(False)
        yield None


It happened to us that someone accidentally made the test method a generator function. That error was caught very late, because it always appears to have executed correctly.

Maybe an additional check can be introduced in the unittest module, to check if a test_ method was executed correctly?