How to Generate Coverage Report with pytest

To generate a coverage report with pytest, install the pytest-cov plugin and run pytest --cov=your_package. Add --cov-report=term or --cov-report=html to see coverage in the terminal or as an HTML report.

Syntax

Use the pytest command with the --cov option to specify the package or module to measure coverage. Add --cov-report to choose the report format.

• --cov=PATH: Path to the code to measure coverage.
• --cov-report=term: Show coverage summary in the terminal.
• --cov-report=html: Generate an HTML report in a htmlcov folder.

bash

pytest --cov=your_package --cov-report=term
pytest --cov=your_package --cov-report=html

Example

This example shows how to run pytest with coverage on a sample package named myapp. It runs tests and prints a coverage summary in the terminal and also creates an HTML report.

python

[test_sample.py]

def add(a, b):
    return a + b


def test_add():
    assert add(2, 3) == 5


# Run this command in terminal:
# pytest --cov=myapp --cov-report=term --cov-report=html

Output

============================= test session starts =============================
collecting ... collected 1 item

test_sample.py .                                                          [100%]

---------- coverage: platform linux, python 3.x.x ----------
Name           Stmts   Miss  Cover
----------------------------------
myapp.py           3      0   100%

============================== 1 passed in 0.03s ==============================

# An HTML report is created in the htmlcov directory.

Common Pitfalls

Common mistakes when generating coverage reports include:

• Not installing pytest-cov plugin, so --cov option is not recognized.
• Forgetting to specify the correct package or module path in --cov=.
• Running tests without coverage options, so no report is generated.
• Expecting coverage for code not imported or executed during tests.

bash

Wrong:
pytest

Right:
pytest --cov=myapp --cov-report=term

Quick Reference

Option	Description
--cov=PATH	Measure coverage for the specified path
--cov-report=term	Show coverage summary in terminal
--cov-report=html	Generate HTML coverage report
--cov-report=xml	Generate XML coverage report for CI tools
--cov-fail-under=MIN	Fail test if coverage is below MIN%

Key Takeaways

Install pytest-cov plugin to enable coverage reporting with pytest.

Use --cov=your_package to specify which code to measure.

Add --cov-report=term or --cov-report=html to see coverage results.

Ensure tests execute the code you want coverage for.

Use --cov-fail-under to enforce minimum coverage thresholds.