pytest：使用假设时的monkeypatch答案

【问题标题】：pytest: monkeypatch while using hypothesispytest：使用假设时的monkeypatch
【发布时间】：2020-12-28 18:35:01
【问题描述】：

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，但在使用pytest 执行以下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 ==============================================================================================================

这是否意味着无论hypothesis生成多少个测试用例，dict的值都只会改变一次？
在这种情况下，我不确定如何使用上下文管理器。有人可以指出我正确的方向吗？

【问题讨论】：

标签： pytest monkeypatching hypothesis-test python-hypothesis

【解决方案1】：

您的问题是 dict 仅针对所有测试调用修补一次，Hypothesis 正在警告您。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，而不是通过夹具：

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，没有警告。

【讨论】：

您的确切代码在我的机器上不起作用。我确实在第 12 行收到了AttributeError: __enter__。您能验证一下吗？
错别字，抱歉 - 应该是 with MonkeyPatch().context() as mp:

【解决方案2】：

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)

【讨论】：

代码正在运行，但是警告并没有消失。这是为什么？我可以确定忽略此警告吗？