Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Testing web apps
Lecture: Special challenges of the web
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And you'll see that there are some special challenges
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to testing web applications.
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They often have more dependencies
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and other systems tangled up in their code than most.
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Here is the register_post method.
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This is the method that we roughly wrote
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when we want to have a user come to the site
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and create an account.
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They're going to go to the form
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where there's a get version that shows in the form.
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They're going to fill it out
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and they're going to hit post.
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This code is going to run.
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What if we want test this behavior?
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Or if we want to verify
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that its user can register for our site
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if that account email address is not already taken
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and all the details are filled out.
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Let's say if the email is not even filled in
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then we get the right error message and so on.
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We want to test this code.
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What are some of the challenges here?
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Well, look carefully.
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Over here in RegisterViewModel
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remember it imports Flask inside
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and it goes flask.request.
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So, implicitly it expects request to be there
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and to be setup and to have values
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and not be empty. Things like that.
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Wen we call vm.validate
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we see it as actually going to request.form
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and we then get to pull out things
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like the full name and the email and so on.
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We need that to be correctly populated.
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In this user service
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when we try to create the account
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it's probably going to the database
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just like Validate also would
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when it wanted to verify that the account
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didn't already exist. This is going to go to the database
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and maybe insert some data if that worked.
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It might also do some other kind of check as well here.
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Maybe it does other things
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like maybe it registers the user
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at some other API
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like for example, adding the user to our mailing list
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or sending them an email.
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We don't want that to happen.
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We don't want any of those things to happen.
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We want to test in isolation.
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We don't want to depend on the database.
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We don't some random user to get an email
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every time we run this automated test.
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Things like that.
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We want to avoid those.
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Here, when we call login
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this is probably working with the response object
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and calling set_cookie.
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Finally, at the end
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we're doing some kind of redirect with Flask.
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What does that need set up to work?
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So, as you can see
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there's a relatively simple function
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has all sorts of tangled interconnections
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with the web framework
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with the database
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and potentially other services
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like email and external APIs.
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How do we test this?
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We'll see that Python and the test frameworks
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have everything that we need to make this work.
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But, it's going to take a little bit of special attention
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and some cool techniques.
