Pytest capsys

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Testing print/log statements in pytest can be a bit tricky, capsys makes it super easy, but I often struggle to find it.

capsys

capsys is a builtin pytest fixture that can be passed into any test to capture stdin/stdout. For a more comprehensive description check out the docs on capsys

using capsys

Simply create a test function that accepts capsys as an argument and pytest will give you a capsys opject.

def test_print(capsys):
    print('hello')
    captured = capsys.readouterr()
    assert 'hello' in captured.out
    print('world')
    captured = capsys.readouterr()
    assert 'world' in captured.out