python: fix instance handling in static and class method tests #12096
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No longer does unittest stuff. Also the rest of the sentence is not really necessary for a docstring.
No need to compute the property multiple times.
and also fixes a regression in pytest 8.0.0 where `setup_method` crashes if the class has static or class method tests. It is allowed to have a test class with static/class methods which request non-static/class method fixtures (including `setup_method` xunit-fixture). I take it as a given that we need to support this somewhat odd scenario (stdlib unittest also supports it). This raises a question -- when a staticmethod test requests a bound fixture, what is that fixture's `self`? stdlib unittest says - a fresh instance for the test. Previously, pytest said - some instance that is shared by all static/class methods. This is definitely broken since it breaks test isolation. Change pytest to behave like stdlib unittest here. In practice, this means stopping to rely on `self.obj.__self__` to get to the instance from the test function's binding. This doesn't work because staticmethods are not bound to anything. Instead, keep the instance explicitly and use that. BTW, I think this will allow us to change `Class`'s fixture collection (`parsefactories`) to happen on the class itself instead of a class instance, allowing us to avoid one class instantiation. But needs more work. Fixes pytest-dev#12065.
nicoddemus
approved these changes
Mar 9, 2024
| assert isinstance(items[1], Function) | ||
| assert items[1].name == "test_method" | ||
| assert items[1].instance is not None | ||
| assert items[1].instance.__class__.__name__ == "TestIt" | ||
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| # Even class and static methods get an instance! |
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I guess it is possible for this to break some plugin which is using instance to check if the method is a static/classmethod, but I suppose this is far fetched.
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You prompted me to check how plugins use instance. Overall it's almost not used, the only prominent case I found is pytest-asyncio, whose usage is not problematic if I'm reading correctly and according to its tests.
pytest-asyncio however was broken by yesterday's removal of FixtureDef.unittest (#12089), for which I will send them a fix.
This was referenced Apr 29, 2024
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and also fixes a regression in pytest 8.0.0 where
setup_methodcrashes if the class has static or class method tests.It is allowed to have a test class with static/class methods which request non-static/class method fixtures (including
setup_methodxunit-fixture). I take it as a given that we need to support this somewhat odd scenario (stdlib unittest also supports it).This raises a question -- when a staticmethod test requests a bound fixture, what is that fixture's
self?stdlib unittest says - a fresh instance for the test.
Previously, pytest said - some instance that is shared by all static/class methods. This is definitely broken since it breaks test isolation.
Change pytest to behave like stdlib unittest here.
In practice, this means stopping to rely on
self.obj.__self__to get to the instance from the test function's binding. This doesn't work because staticmethods are not bound to anything.Instead, keep the instance explicitly and use that.
BTW, I think this will allow us to change
Class's fixture collection (parsefactories) to happen on the class itself instead of a class instance, allowing us to avoid one class instantiation. But needs more work.Fixes #12065.