Run unittest.main() from a python invoke task

I am trying to run some unittest tests via a Python Invoke library, but my poor knowledge of Python prevents me from doing so.

This is the sample code I have:

my_tests.py

import unittest

class TestStringMethods(unittest.TestCase):

    def test_upper(self):
        self.assertEqual('foo'.upper(), 'FOO')

    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())

    def test_split(self):
        s = 'hello world'
        self.assertEqual(s.split(), ['hello', 'world'])
        # check that s.split fails when the separator is not a string
        with self.assertRaises(TypeError):
            s.split(2)

def main():
    unittest.main()

if __name__ == '__main__':
    main()

tasks.py

from invoke import task

@task
def tests(ctx):
    main()

@task
def other_task(ctx):
    print("This is fine")

def main():
    import my_tests
    import unittest
    unittest.main(module='my_tests')

if __name__ == '__main__':
    main()

And this is what I get:

C:\ittle_projects\invoke_unittest>python my_tests.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.002s

OK

C:\ittle_projects\invoke_unittest>python tasks.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.001s

OK

C:\ittle_projects\invoke_unittest>inv tests
E
======================================================================
ERROR: tests (unittest.loader._FailedTest)
----------------------------------------------------------------------
AttributeError: module 'my_tests' has no attribute 'tests'

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)

The tests run fine from my_tests.py and from tasks.py, but when I use invoke stuff breaks. How can I make it work or where should I look next?

The issue you are running into is that unittest.main() uses the command line arguments your program is called with to determine which tests to run. Since your program is being executed as inv tests, the first argument to your program is tests, so unittest is attempting to run tests for a module name tests which does not exist.

You can get around this by popping the last argument (tests) from the system arguments list:

import sys

from invoke import task

@task
def tests(ctx):
    # Pop "tests" off the end of the system arguments
    sys.argv.pop()
    main()

@task
def other_task(ctx):
    print("This is fine")

def main():
    import my_tests
    import unittest
    unittest.main(module='my_tests')

if __name__ == '__main__':
    main()