Building Data-Driven Web Apps with Flask and SQLAlchemy Transcripts
Chapter: Testing web apps
Lecture: Concept Testing view methods
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Now let's move up one level
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in the amount that we're testing at once
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and the part of the application that we're testing.
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'Cause we're using view models
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we can basically assume
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that all the validation is working just fine
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and the data exchange is working fine
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as long as we test that
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but what we do need to test
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is that the view method
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is working with the view model's response correctly.
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If an error comes back
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that it actually shows the page with an error
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rather than just ignores it
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or that if it uses that data
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to try to create our user
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if that user can't be created
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it still shows the error
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instead of just redirecting you.
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Things like that.
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So, that's the layer we just tested
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and we're going to review right now.
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So, we're going to test the home page
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and we're just going to ignore the database aspect
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for just a moment.
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We'll see a more realistic one in a second.
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So, let's imagine that we don't need
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to talk to the database
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we're going to come in here
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we're going to import the index view method from home views
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and we're going to create a context manager
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that is a test request just to slash.
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Then we're going to do act
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which is simply to call the function
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and capture the response
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so what we get back from these Flask methods
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is always a response
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and then we want to do some kind of assert
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like that the status code is 200
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and that the model contains packages
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and that the length
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because that's a list, the length of it
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is greater than zero.
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Right, that part actually probably came from the database
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so keeping it simple right now.
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But this is a totally reasonable test
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that we might write for the index home page.
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One quick side note that model
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on the response, that is set by the @response decorator
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that I created for this course
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where you automatically have it pick up the view template.
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If you don't do that
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you have to find another day to capture that data.
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You can look in the decorator, see how it's done there
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and so on, all right?
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So, we have this and it looks like it's working.
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It does work just fine
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but if we want a more realistic version
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well, we need more space
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because this time we don't want to talk to the database
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and we're going to talk to a fairly complicated function.
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We haven't seen this test written yet
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so imagine we want to test
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if we go to our package details page.
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I want to go to like /project/sqlalchemy
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and see what comes back
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but actually not talk to the database.
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Come over here, we're going to import project
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the method project from the package views
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and we're going to import the Package object itself
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because we're going to have to create some test data
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that we can then mock out
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so the project view gets that from the mocked method calls.
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Then we're going to create our test package
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I'm going to set the id to sqlalchemy
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we're going to give it a couple of releases.
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The reason we want a beta release is because the
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basically that package method assumes
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that there are releases.
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And then we'll going to mock a bunch of stuff out
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we're going to say if you call package
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package_service.get_package_by_id, you get this test SQLAlchemy package.
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If you all releases for package
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you get the releases that we set here
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and the context is going to be set to /project/sqlalchemy.
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The next thing to do is act.
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We're going to call our project function
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and remember, in Flask, it takes the argument
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right, it's up to the Flask infrastructure
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to pass that along
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but we're calling it directly
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so it's now our job to pass that along
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and internally, that's going to be calling get package by ID
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form package service and all the other stuff that happens inside.
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That's why we had to mock it up.
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And then we can just assert.
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I say the web package, the one that we got back
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inside the model
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we're going to capture it
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and I'm going to ask some questions.
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Is the package.id actually sqlalchemy
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and does it actually have two releases?
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So, like this, we can do legitimate tests
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against complex methods
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that interact with the database
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and inbound arguments, all that kind of stuff.
