Testing coverage

Test Coverage

pip install coverage

Use coverage run to run your test suite and gather data. However you normally run your test suite, you can run your test runner under coverage. If your test runner command starts with “python”, just replace the initial “python” with “coverage run”.

Pytest

If you usually use:

pytest arg1 arg2 arg3

then you can run your tests under coverage with:

coverage run -m pytest arg1 arg2 arg3

Unittest

Change “python” to “coverage run”, so this:

python -m unittest discover

coverage run -m unittest discover

To limit coverage measurement to code in the current directory, and also find files that weren’t executed at all, add the --source=. argument to your coverage command line.

Report

Use coverage report to report on the results:

coverage report -m
Name                      Stmts   Miss  Cover   Missing
-------------------------------------------------------
my_program.py                20      4    80%   33-35, 39
my_other_module.py           56      6    89%   17-23
-------------------------------------------------------
TOTAL                        76     10    87%

For a nicer presentation, use coverage html to get annotated HTML listings detailing missed lines:

coverage html

Then open htmlcov/index.html in your browser, to see a report like this.

Coverage measurement is typically used to measure the effectiveness of tests. It can show which parts of your code are being processed by tests and which are not.

You can use the сoverage.py tool for measuring code coverage. It monitors your program, recording which code parts have been executed, then analyzes the code that could have been executed but was not.

To run coverage measurement:

use the coverage run command to run your test and collect the data. However, you normally run your test, you can run your test runner under coverage. If normally your test execution command starts with the python, you replace the initial python with the coverage run — coverage run -m pytest, then use the coverage report to report on the results:

$ coverage report
Name              Stmts   Miss  Cover   Missing
-----------------------------------------------------------
main.py           7       3     57%        8-10
test_main.py      6       0     100%
-----------------------------------------------------------
TOTAL             13      3     77%

for PyCharm Pro, click the Run with Coverage button on the main toolbar. This will launch the selected run/debug configuration:

![[coverage_button.png.webp]]