pytest: AssertionError inside Context Manager not raised

user_2606766 0
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There are some similar questions, e.g Pytests with context manager. Still I don't get it. Why is this assertion inside a context manager not raised?

class foo:
    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        return self

def test_context_manager():
    with foo():
        assert False  # <- works outside the with statement but not here

Using: python3.9 and pytest6.2.5

Update: it works when the __exit__ method of the context manager does not return self. This works:

class foo:
    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        pass  # <- this fixes it

But still the question remains. Why does the 1st case fail. Is this a bug? Shall I report it?

pytest contextmanager python-3.x python
1 Answers

A context manager is designed to catch exceptions like this and pass it to __exit__. If you want to raise the exception, you need to take care of it yourself:

class foo:
    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        if exc_value:
            raise exc_value # AssertionError raised here
        return self

def test_context_manager():
    with foo():
        assert False

test_context_manager()
user_144121900
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