How to use logging, pytest fixture and capsys?

Question

I am trying to unit-test some algorithm that uses logging library.

I have a fixture that creates a logger.

In my 1st test case, I do not use

Answer 1

As of pytest 3.3, the functionality of capturing log message was added to pytest core. This is supported by the caplog fixture:

def test_baz(caplog):
    func_under_test()
    for record in caplog.records:
        assert record.levelname != 'CRITICAL'
    assert 'wally' not in caplog.text

More information can be found at the documentation