49 lines
2.1 KiB
Markdown
49 lines
2.1 KiB
Markdown
---
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title: "How to reset a mocked object during test ? - Python"
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date: 2018-02-22
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layout: post
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category: Programming
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image: /img/blog/how-to-reset-a-mocked-object-during-test-python.png
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description: "Unittest appears to be such a pain to work with... Let's see if we can figure something out !"
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---
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I don't know if this post title is good enough, but that is something I was facing some days ago :
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[](/img/blog/how-to-reset-a-mocked-object-during-test-python.png)
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The problem here can be described as below :
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* We'd like to mock the first (or the last ?) `Popen` call, to test the chained external calls logic
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* We can't mock _totally_ `Popen`, because each call would return the same thing, and this is not what we want here
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* There is exactly the same problem with `check_output` calls (the first one has to fail, whereas the second one should have its "default" behavior)
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* These calls happen during the **same tested method**, so it's not possible to reset the mock like some persons use to do :
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{% highlight python %}
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p = patch("module.object", new=MagicMock(return_value="Blah"))
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p.start()
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self.assertTrue(methodToTest())
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p.stop()
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self.assertFalse(methodToTest())
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{% endhighlight %}
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So I've tried something, based upon [this StackOverflow thread](https://stackoverflow.com/questions/15751467/unittest-python-mock-only-one-function-multiple-call/15752019#15752019), and the result was impressive after some struggles, as expected :smirk:
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The idea is :
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* Mock the object you want to mock with a new object **you control**
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* This new object will behave in function of an internal state that **you set**
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* Decide when you want to mock this object with a "patched" entity, or let it act with its default behavior !
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> So let's stop endless sentences and present a **working** solution please !
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>> Yeah, you'll find below a simple use case to illustrate this principle :
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<script src="https://gist.github.com/HorlogeSkynet/6f41e58fa30fe3da90f9804ab5983d5e.js"></script>
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