How to improve pytest performance by clearing pytest cache and results in VSCode

The aim of this page📝 is to explain how to clear pytest results and cache in Visual Studio Code based on the particular example of improving pytest performance. I was motivated to look into this because tests on a single module (say 20 tests) ran 10 seconds. Then I saw Dynamic run result in test explorer for pytest · Issue #21148 · microsoft/vscode-python. The best improvement came from simply running Clear all results, but try clearing cache, too.

2 min readAug 14, 2023

The pytest cache is used to store data between test runs, such as the results of expensive computations or the state of external resources.
Clearing the cache can improve performance by ensuring that tests are run with a clean slate.
The --cache-clear flag can be used when running pytest to clear the cache at the start of the test run.
In Visual Studio Code, you can add the --cache-clear flag to your pytest configuration by opening the Command Palette and selecting Python: Configure Tests.
Then, select the pytest test framework and the root directory containing your tests.
In the settings.json file, find the "python.testing.pytestArgs" setting and add "--cache-clear" to the list of arguments.

{
    "python.testing.pytestEnabled": true,
    "python.testing.pytestArgs": [
        "--cache-clear"
    ]
}

The Test Explorer in Visual Studio Code provides an interface for running and debugging tests and analyzing test results.
Clearing test results in the Test Explorer does not clear the pytest cache
It also should not affect test performance — but in my case it did as I have not done that in months
Test results can be cleared manually by clicking on the “Clear all results” button in the Test Explorer or by running the “Clear all results” command from the Command Palette.
Currently (unfortuntelly in my case), there is no built-in way to automatically clear test results in the Visual Studio Code Test Explorer.