Unittest tests will not run with `unittest.main()` in the test file

[TheCatSaber]

Environment data

• VS Code version: 1.60.0 (user setup) (Commit: e7d7e9a9348e6a8cc8c03f877d39cb72e5dfb1ff)
• Extension version (available under the Extensions sidebar): v2021.9.1191016588
• OS and version: Windows_NT x64 10.0.19042
• Python version (& distribution if applicable, e.g. Anaconda): 3.9.7
• Type of virtual environment used N/A
• Value of the python.languageServer setting: Pylance

Expected behaviour

When you run the tests from the Testing side bar in the extension, tests run properly when you have unittest.main() in a file.

Actual behaviour

Unittest Discovery Error [Folder Name]
Error discovering unittest tests (see Output > Python):

(with nothing in Output > Python).

Steps to reproduce:

[NOTE: Self-contained, minimal reproducing code samples are extremely helpful and will expedite addressing your issue]

1. Create a new folder, and create add.py and test.py
2. In add.py put:

def add(a, b):
    return a + b

3. In tests.py put:

import unittest
from add import add

class TestAdd(unitest.TestCase):
    def test_one_plus_one(self):
        self.assertEqual(2, add(1, 1))

4. Using Testing on the sidebar select Set-up python tests > unittest > . > test*.py
5. Run the tests, tests work normally ✅
6. Add unitest.main() to the bottom of test.py.
7. Run test.py with python test.py: tests work normally ✅
8. Try running tests with the Testing side bar: tests do not work, and you get the error described above ❌

Logs

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

None

[karthiknadig]

If you use unittest.main() then that can try to execute tests when the unittest loader loads this. So this should work better if you protect it like this. This is the recommended way of protecting code from running on import.

if __name__ == '__main__':
    unittest.main()

[TheCatSaber]

1. I should have been doing if __name__ == '__main__': anyway.
2. That fixed the problem.

I think it would be a good idea to make the error more explicit (i.e. to try to detect the running of the tests, and output a message to the user, saying to use if __name__ == '__main__').

[brettcannon]

We are working on rewriting our detection/execution code which should simply ignore the initial run as a side-effect of importing.

[karthiknadig]

Closing in favor of #17242