How to run unittest tests using coverage API

Question

I am trying to generate a coverage report using the coverage -API ( https://coverage.readthedocs.io/en/6.3.2/api.html#api ).

The simple use-case described on the linked page tells me to wrap my executed code inside the snippet they provide. I am using unittest.main() to execute tests. The below code runs without an error but neither is any report information created nor is print("Done.") executed.

I guess unittest.main() calls a sys.exit() somewhere along the way? How does one use the API to execute all unittest-tests?

Example

import coverage
import unittest


def func(input):
    return input


class testInput(unittest.TestCase):
    def test_func(self):
        self.assertEqual(func(1), 1)

    
if __name__ == '__main__':
    cov = coverage.Coverage()
    cov.start()

    unittest.main()

    cov.stop()
    cov.save()

    cov.html_report()
    print("Done.")

Answer 1

Yes, it looks like unittest.main() is calling sys.exit(). Are you sure you need to use the coverage API? You can skip coverage and most of unittest:

# foo.py
import unittest


def func(input):
    return input


class testInput(unittest.TestCase):
    def test_func(self):
        self.assertEqual(func(1), 1)

Then:

$ python -m coverage run -m unittest foo.py
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

$ python -m coverage report -m
Name     Stmts   Miss  Cover   Missing
--------------------------------------
foo.py       6      0   100%
--------------------------------------
TOTAL        6      0   100%

Answer 2

To get the example to work you can simply put the call to unittest.main() in a try/except statement so the cov.stop() will be called once the unit test has completed.

# testInput.py
import coverage
import unittest

def func(input):
    return input

class testInput(unittest.TestCase):
    def test_func(self):
        self.assertEqual(func(1), 1)

if __name__ == '__main__':
    cov = coverage.Coverage()
    cov.start()

    try:
        unittest.main()
    except:  # catch-all except clause
        pass

    cov.stop()
    cov.save()

    cov.html_report()
    print("Done.")

This will run as desired, including printing Done. at the end:

python3 testInput.py 
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
Done.

The HTML coverage report will have been created in the htmlcov directory in the current working directory.