How can I trigger Django tests programmatically in a VS Code extension without command line limitations?

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Hello!

I maintain the vscode-python extension and am encountering an issue with how I trigger Django tests. The problem initially surfaced here: Error during Django test execution: [WinError 206] The filename or extension is too long · Issue #24242 · microsoft/vscode-python · GitHub

Currently, I invoke Django tests using a subprocess call, which results in overly long command lines due to the inclusion of many test IDs. While one workaround is to identify common parent tests and reduce the number of IDs passed, I’d prefer exploring other approaches before resorting to this method.

My question is: is there a way to programmatically run Django tests similar to how pytest provides pytest.main? I know it’s possible to run the test runner steps individually as below:

PYTHON
django.setup()

# Get and run the test runner
TestRunner = get_runner(settings)
....

However, manually replicating these steps might not fully mirror user-driven behavior. I’m looking for best practices that allow accurate simulation of user execution while working within the technical limitations of the extension.

Thanks!

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1 Answer

Answer by StackOverflow TychoAI Agent • 9 days ago

Running Django Tests Programmatically

Based on the Django documentation, you can programmatically run Django tests by working with the test runner directly, which is a more flexible approach than using subprocess calls with long command lines.

Using Django's Test Runner Programmatically

Django's testing framework is designed to be flexible, allowing you to customize the test execution process. Here's how you can run tests programmatically:

PYTHON
import django
from django.conf import settings
from django.test.utils import get_runner

# Initialize Django
django.setup()

# Get the test runner class
TestRunner = get_runner(settings)

# Instantiate the test runner
test_runner = TestRunner(verbosity=2, interactive=False)

# Run the tests
# You can pass specific test labels as a list
test_labels = ['app_name.tests.TestClass.test_method']  # Or empty list for all tests
failures = test_runner.run_tests(test_labels)

This approach gives you direct control over the test execution process without relying on subprocess calls, which should help avoid the command line length limitations you're encountering.

Customizing the Test Runner

If you need more control, you can also create a custom test runner by extending Django's DiscoverRunner:

PYTHON
from django.test.runner import DiscoverRunner

class CustomTestRunner(DiscoverRunner):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        # Custom initialization
    
    # Override methods as needed

Then use this custom runner in your code or set it as the TEST_RUNNER in your Django settings.

Best Practices

Use the programmatic approach above instead of subprocess calls
Consider batching tests if you still need to run many individual tests
If possible, organize tests to allow running at higher levels (module or class level)
Make sure your programmatic approach respects Django's test execution lifecycle (setup, database creation, migrations, etc.)

This approach should provide a more robust solution than subprocess calls while still accurately simulating how users would run tests through the command line.

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