How to Efficiently Carry Over Variables from Pytest Fixtures to Tests

Описание: Learn how to pass variables from pytest fixtures to your test functions using yield statements effectively. Discover best practices for cleaner, more maintainable code!
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This video is based on the question https://stackoverflow.com/q/68317135/ asked by the user 'Kintarō' ( https://stackoverflow.com/u/1701504/ ) and on the answer https://stackoverflow.com/a/68317549/ provided by the user 'Jason Cook' ( https://stackoverflow.com/u/8672714/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Efficiently Carry Over Variables from Pytest Fixtures to Tests

When working with testing frameworks in Python, such as pytest, you may often find yourself needing to set up certain conditions or configurations before running your tests. One common scenario is when you have a pytest fixture that creates resources (like a Kinesis stream) and you need to access that resource (its name, for instance) in your actual test functions.

The Problem

You might be facing a situation where your setup and teardown process is properly laid out in a fixture, but you need to pass a variable from that fixture to your test functions. Here’s an excerpt from a typical setup:

[[See Video to Reveal this Text or Code Snippet]]

In this case, you need to access stream_name within your tests test_func1 and test_func2, but you can't use global variables since each test should maintain its own unique stream. So how do we elegantly pass stream_name to the test functions?

The Solution

The solution is simpler than you might think! By modifying your fixture to yield the stream_name, and then passing that value directly to your test functions as a parameter, you can achieve the desired results.

Here’s a step-by-step breakdown:

Step 1: Modify the Fixture

Update your fixture to yield the stream_name instead of just completing the resource setup. This way, the stream name becomes part of the fixture's return value.

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Adjust the Test Functions

Now, update your test functions to accept the fixture as an argument. This will give you access to the stream_name directly:

[[See Video to Reveal this Text or Code Snippet]]

Why This Works

Yielding the Value: By yielding stream_name, the fixture allows the test function to have access to it when called.

Scoped Variables: Each test invocation will get its own unique stream_name because the fixture is executed separately for each test.

Cleaner Code: This method avoids the pitfalls of global variables and keeps your tests clean and maintainable.

Conclusion

Passing variables from pytest fixtures to test functions not only makes your tests more reliable but also keeps them clean and organized. The approach of yielding values from fixtures is a powerful feature of pytest that can greatly enhance your testing strategy.

Start integrating this practice into your pytest setup, and experience the difference in both code quality and test reliability!