Getting started with pytest Transcripts
Chapter: Test Functions
Lecture: Structuring test functions
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I want to take a break and talk about test structure for a minute. All the tests that we're writing so far kind of fall into a similar structure with
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the asserts at the bottom. And that's not on accident. So let's grab one of these test to dict and talk about it specifically.
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We'll stick it over here and just so that we can run it if we want So here's our test. And the structure comes in several forms and it's been
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it's been talked about by Kent, Beck and Dan north and many others. as either Arrange, Act, Assert or Given, When, Then.
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So let's talk about Arrange Act Assert at first. So at the top of the test we're gonna arrange whatever we need to arrange and
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then we're going to do an action and then then we'll assert some stuff. How does that look like in our tests? So in our test we've got c1.
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we created a card. This isn't this is just kind of getting ready to do an action. So this would be the arrange.
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And then the action we're testing is 'to dict'. We want to see what 'to Dict' does so to dict is the action.
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And then the assertion at the end is this bottom bit where we have I think the expected value creation is part of the assertion.
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So we've got the assert here and a lot of people really really kind of resonate with the arrange act assert idea.
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So if arrange act assert works for you to keep these in kind of a good order. That's great. The main thing we wanna do is we want to
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keep the arranging stuff at the top. With no asserts. Hopefully the act obvious and the act should be kind of obvious
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from the test name as well hopefully. And then the assertions at the bottom. What we don't want to do is inter leave these.
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We don't want to start doing multiple actions interleague with asserts.
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Because those are difficult. What resonates more with me is given when then so let's take a look at what that would be like.
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So given a card with known value when when we call to dict on the card
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then we get the expected dictionary. The reason why I really like the given when then model of it. It's the same as Arrange Act Assert.
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It's just I like thinking about a given state. So given a certain state when I do some action then some expected outcome happens.
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I like this because then I can come up with different given states. So for a particular action, what are the all the different states that I need
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to act on? And then for a given action, what sort of maybe what sort of expected outcomes could I get even if I come
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up with different states? And this sort of thinking helps me. And so for me I usually think and given when then and not Arrange Act Assert
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but really either one if it works for you then awesome.