Avoiding File Overwrites with pytest

Welcome to another insightful post where we discuss about improving your development practices with Python!

The Problem: Overwriting Test Results

This can be particularly frustrating when you’re trying to diagnose intermittent failures or track changes in test outcomes over time.

This approach can be beneficial in environments where an AI code editor like Code LM could monitor test failures in real-time, leveraging the capabilities of large language models in code generation and testing.

The Solution: Unique Output Files

To tackle this, we can modify the script to generate unique output files for each test run.

How It Works

• File Prefix: We use OUTPUT_PREFIX to set a common prefix for our output files, ensuring they’re easily identifiable as part of the same test series.
• Loop: The script runs in an infinite loop (while true), incrementing i each time to create a new file name (pytest_output_1.txt, pytest_output_2.txt, etc.).
• Pytest Command: Each iteration runs pytest with options to capture system output (--capture=sys) and specifies the output file dynamically using the counter i.

Benefits

• No Overwriting: Each test run’s results are saved to a new file, preserving all test data for review.
• Easier Analysis: With separate files, you can easily compare different runs, track down when issues started occurring, or analyze performance over time.
• Automation Friendly: This setup is perfect for automated environments where tests are run periodically, allowing for a historical record of test outcomes.

Conclusion

This small tweak to Tom Dörr’s original concept not only solves the problem of overwriting but also enhances your testing workflow by providing clear, organized, and historical data on your tests.

# Set output file prefix
OUTPUT_PREFIX=”pytest_output_”

# Run pytest in a loop with one thread
i=1
while true; do
echo “——————–“
echo “Running pytest…”
echo “——————–” > “${OUTPUT_PREFIX}${i}.txt”

# Run pytest and append output directly to the new file
pytest -n 1 –capture=sys -o “output_file=${OUTPUT_PREFIX}${i}.txt” tests

echo “Pytest completed. Waiting 5 seconds before next run…”
sleep 5
((i++))
done

Remember, in your actual implementation, adjust the tests directory in the pytest command to match your project’s structure. Keep testing, keep improving!

Thank you, Tom, for the inspiration! If you’re interested in more tips like this, keep following our blog for regular updates on Python development best practices. Happy coding! 🧪✨