Understanding python coverage with practically

 

Python Coverage refers to measuring which parts of your Python code are being executed during testing. It is a critical tool for ensuring comprehensive test coverage, helping developers understand which lines of code are tested and which are not. Here’s a deeper dive into how to use Python Coverage effectively:

Getting Started with Python Coverage

1. Installation

You can install the coverage module using pip:

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pip install coverage

2. Running Tests with Coverage

To measure code coverage, you run your tests through the coverage tool. Here’s a basic example:

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coverage run -m unittest discover

This command runs all tests discovered by unittest while tracking code coverage.

3. Generating Coverage Report

After running tests, you can generate a coverage report. Coverage provides different report formats, including terminal output, HTML, and XML. Here’s how to generate a simple text report:

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coverage report

For a more detailed HTML report, use:

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coverage html

This will create an htmlcov directory with the coverage report. You can open index.html in a browser to view the report.

4. Configuring Coverage

You can configure coverage settings in a .coveragerc file. Here’s an example configuration:

ini

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[run]

branch = True

source = my_package

 

[report]

show_missing = True

• branch: Ensures branch coverage is measured.
• source: Specifies the source code directories.
• show_missing: Displays lines that were not executed.

5. Advanced Usage

• Excluding Files: To exclude files or directories from coverage, use the omit option in the .coveragerc file:

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[run]

omit =

    */tests/*

    */migrations/*

• Combining Coverage Data: To merge coverage data from multiple runs, use:

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coverage combine

• Checking Coverage Thresholds: Set minimum coverage thresholds to enforce code quality:

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coverage report --fail-under=80

This command will fail the build if the coverage is below 80%.

Example Usage

Here’s a complete example of running tests with coverage and generating a report:

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# Install coverage

pip install coverage

 

# Run tests with coverage

coverage run -m unittest discover

 

# Generate a terminal report

coverage report

 

# Generate an HTML report

coverage html

Conclusion

Python Coverage is a powerful tool for ensuring your tests cover all parts of your codebase. By integrating it into your development workflow, you can improve code quality, catch bugs early, and maintain high test coverage standards. Happy coding!