pytest：使用假设时的monkeypatch

Question

在单元测试中，我使用 monkeypatch 来更改 dict 中的条目。

from hypothesis import given, strategies
    
    
test_dict = {"first": "text1", "second": "text2"}
    
    
given(val=strategies.text())
def test_monkeypath(monkeypatch, val):
    monkeypatch.setitem(test_dict, "second", val)
    
    assert isinstance(test_dict["second"], str)

测试通过了，但是在用pytest执行下面的测试代码时收到警告。

=================================================================================================================== warnings summary ====================================================================================================================
.PyCharm2019.2/config/scratches/hypothesis_monkeypatch.py::test_monkeypath
  c:\users\d292498\appdata\local\conda\conda\envs\pybt\lib\site-packages\hypothesis\extra\pytestplugin.py:172: HypothesisDeprecationWarning: .PyCharm2019.2/config/scratches/hypothesis_monkeypatch.py::test_monkeypath uses the 'monkeypatch' fixture, wh
ich is reset between function calls but not between test cases generated by `@given(...)`.  You can change it to a module- or session-scoped fixture if it is safe to reuse; if not we recommend using a context manager inside your test function.  See h
ttps://docs.pytest.org/en/latest/fixture.html#sharing-test-data for details on fixture scope.
    note_deprecation(

-- Docs: https://docs.pytest.org/en/stable/warnings.html
============================================================================================================= 1 passed, 1 warning in 0.30s ==============================================================================================================

这是否意味着dict的值只会改变一次，无论hypothesis会生成多少测试用例？
我不确定在这种情况下如何使用上下文管理器。有人可以给我指出正确的方向吗？

Answer 1

使用monkeypatch context manager

@given(val=strategies.text())
def test_monkeypath(monkeypatch, val):
    with monkeypatch.context() as m:
        m.setitem(test_dict, "second", val)

        assert isinstance(test_dict["second"], str)

Answer 2

你的问题是字典只为所有测试调用打了一次补丁，Hypothesis 就此警告你。如果您在 monkeypatch.setitem 行之前有任何逻辑，那就太糟糕了！

您可以通过 using monkeypatch directly 解决此问题，而不是通过固定装置：

from hypothesis import given, strategies
from _pytest.monkeypatch import MonkeyPatch


test_dict = {"first": "text1", "second": "text2"}


@given(val=strategies.text())
def test_monkeypath(val):
    assert test_dict["second"] == "text2"  # this would fail in your version

    with MonkeyPatch().context() as mp:
        mp.setitem(test_dict, "second", val)
        assert test_dict["second"] == val

    assert test_dict["second"] == "text2"

瞧瞧，没有警告。

pytest：使用假设时的monkeypatch

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