[Python] Mock patch sys.stdout to StringIO as a decorator (Python)

I am trying to mock.patch sys.stdout to StringIO as a decorator to record the output for testing.

As a 'with' statement it works this way:

with mock.patch('sys.stdout', new_callable = StringIO) as recorded_output:
print('OUTPUT')
r = recorded_output.getvalue()
print(r)


gets 'OUTPUT', but 'getvalue' doesn't work when used as a decorator:

@mock.patch('sys.stdout', new_callable = StringIO)
def test_stdout(self, recorded_output):
print('OUTPUT')
r = recorded_output.getvalue()
print(r)


gets error: Mock object has no attribute 'getvalue'

Does anyone know how to write this as a decorator?

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