TIL: Tornado | Fix "tornado.util.TimeoutError: Operation timed out after 5 seconds"

Story

Whenever I debug my test for tornado code in the end I get this error

...
> raise TimeoutError('Operation timed out after %s seconds' % timeout)
E tornado.util.TimeoutError: Operation timed out after 5 seconds

.venv/lib/python3.7/site-packages/tornado/ioloop.py:575: TimeoutError

Question

How to fix tornado.util.TimeoutError: Operation timed out after 5 seconds on tornado test debug?

Answer

This is due ASYNC_TEST_TIMEOUT environment variable
From docs

In the event of a timeout, an exception will be thrown. The default timeout is 5 seconds; it may be overridden with a timeout keyword argument or globally with the ASYNC_TEST_TIMEOUT environment variable.

And could be fixed by setting this variable to a bigger value in seconds

$ # running tests with ASYNC_TEST_TIMEOUT set to 10 minutes
$ ASYNC_TEST_TIMEOUT=600 python -m unittest

or if you are using pytest with pytest-tornado plugin by passing --async-test-timeout argument to pytest command

$ pytest --async-test-timeout=600

Links

• https://www.tornadoweb.org/en/stable/testing.html#tornado.testing.AsyncTestCase.wait
• https://stackoverflow.com/a/49149757/3627387