bpo-46425: fix direct invocation of asyncio tests

[sobolevn]

Right now some tests in test_asyncio are suitable to be executed directly as python Lib/test/test_asyncio/test_X.py and some are only executable with -m test or -m Lib/test/test_asyncio.

• Supports all styles:

  cpython/Lib/test/test_asyncio/test_asyncio_waitfor.py

  Lines 60 to 61 in c02e860

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

• Does not support direct invocation:

  cpython/Lib/test/test_asyncio/test_context.py

  Lines 33 to 34 in c02e860

  	self.assertEqual(str(r2[0]), '0.333333')
  	self.assertEqual(str(r2[1]), '0.111111')

This does not look good to me.

So, I've fixed several tests modules in test_asyncio when invoked directly as python module_name.py

There were two major problems:

• relative imports
• missing unittest.main() call

The best way to illustrate this problem is to show Lib/test/test_asyncio/test_runners.py:

Step 1. No changes.

» ./python.exe Lib/test/test_asyncio/test_runners.py
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_asyncio/test_runners.py", line 5, in <module>
    from . import utils as test_utils
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ImportError: attempted relative import with no known parent package

Step 2. Fixed relative import.

» ./python.exe Lib/test/test_asyncio/test_runners.py

(nothing happens)

Step 3. With unottest.main():

» ./python.exe Lib/test/test_asyncio/test_runners.py
........
----------------------------------------------------------------------
Ran 8 tests in 0.018s

OK

CC @corona10 as my mentor.

https://bugs.python.org/issue46425

[kumaraditya303]

Is there a reason that you run tests like scripts?

[sobolevn]

Is there a reason that you run tests like scripts?

I just click "Run file" in my IDE, it is the easiest thing to do when testing something.
And since it is supported by if __name__ == '__main__': unittest.main(), I think others might do the same / similar thing.

[asvetlov]

Historically unittest.main() was added on demand during unit tests debugging.
Thanks for spreading it everywhere.

[miss-islington]

Thanks @sobolevn for the PR, and @asvetlov for merging it 🌮🎉.. I'm working now to backport this PR to: 3.9, 3.10.
🐍🍒⛏🤖

[bedevere-bot]

@asvetlov: Please replace # with GH- in the commit message next time. Thanks!

[bedevere-bot]

GH-30782 is a backport of this pull request to the 3.10 branch.

[bedevere-bot]

GH-30783 is a backport of this pull request to the 3.9 branch.