Getting started with pytest Transcripts
Chapter: pytest Fixtures
Lecture: Using fixtures to pass test data
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0:00
As the first example of fixtures, I'm gonna take this simple test, I've got test cube, which checks, I've got a number 42. So this is my given stage.
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I assigned 42 to a number and then I'm taking the cube root of that number with the star star and then I expect it to be the same as multiplying
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the number three times. And so I'm asserting here, given a number is 42. When I cube it the output,
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I assert that the output is going to be the same as multiplying it three by itself three times. This is not that complicated but let's go
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ahead and run it just to make sure it works. So yes that passes, this is not a surprise to us. What happens if we, you know,
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do something else? Let's not the same as four times. Yes. Just make sure that we understand that that fails and that's a pretty big
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number. Okay, put that back to normal. Clear now. How can fixtures help here? Well, the 42 getting ready is right in the test,
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we could push it out of the test and this is a kind of a simple example but I wanted to show you the structure of how we use fixtures.
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So we have to import pytest first and then we use a decorator called
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pytest fixture and just decorate a function and it can be really any function and the return value, it does action and it has a return value.
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If you don't return anything of course and python it returns none. But here we want to return the value because it's going to be used by the
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test and we just put the name of the fixture right is a parameter to the test and when the test runs,
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so pytest is gonna see this and it is gonna see the num and it's gonna say, hey I need a fixture called that. So it's going to find this num fixture.
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Run that take the return value and fill it in for the parameter. It seems kind of cool and it is cool.
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So let's try to run that just to make sure that works. Pytest test cube.py, no just cube fix. Yeah,
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that works too. In this case it doesn't make a lot of sense to pull this out I am just showing the structure of how to use fixture.