Coverage.py: Python Code Coverage from Setup to CI Integration

pip install coverage pytest-cov

# Coverage for the 'myapp' package
pytest --cov=myapp tests/

# Show missing lines in terminal
pytest --cov=myapp --cov-report=term-missing tests/

# Generate HTML report
pytest --cov=myapp --cov-report=html tests/
# Open: htmlcov/index.html

# Fail if coverage drops below 80%
pytest --cov=myapp --cov-fail-under=80 tests/

# .coveragerc
[run]
source = myapp
branch = True          # Enable branch coverage
omit =
    */migrations/*
    */tests/*
    */conftest.py
    */__init__.py
    */manage.py         # Django management commands

[report]
precision = 2
show_missing = True
skip_covered = False
fail_under = 80

[html]
directory = htmlcov
title = MyApp Coverage Report

[xml]
output = coverage.xml

pytest --cov --cov-report=html --cov-report=xml

[tool.coverage.run]
source = ["myapp"]
branch = true
omit = [
    "*/migrations/*",
    "*/tests/*",
    "*/conftest.py",
]

[tool.coverage.report]
precision = 2
show_missing = true
fail_under = 80
exclude_lines = [
    "pragma: no cover",
    "def __repr__",
    "if TYPE_CHECKING:",
    "raise NotImplementedError",
    "@(abc\\.)?abstractmethod",
]

[tool.coverage.html]
directory = "htmlcov"

[tool.coverage.xml]
output = "coverage.xml"

def process_order(order):
    if order.status == "pending":    # ← branch 1: status == pending
        validate(order)
        if order.total > 1000:       # ← branch 2a: total > 1000
            apply_discount(order)    # ← branch 2b: total <= 1000 (never tested?)
    else:                            # ← branch 1b: status != pending
        raise ValueError("Invalid status")
    return order

pytest --cov=myapp --cov-branch --cov-report=html tests/

def __repr__(self):
    return f"Order({self.id})"  # pragma: no cover

class AbstractProcessor:
    def process(self):
        raise NotImplementedError  # pragma: no cover

if TYPE_CHECKING:                  # pragma: no cover
    from myapp.types import Config

# Platform-specific code
if sys.platform == "win32":       # pragma: no cover
    def get_temp_dir():
        return os.environ["TEMP"]

[tool.coverage.report]
exclude_lines = [
    "pragma: no cover",
    "def __repr__",
    "def __str__",
    "if __name__ == .__main__.:",
    "if TYPE_CHECKING:",
    "raise NotImplementedError",
    "pass",
    "@(abc\\.)?abstractmethod",
    "\\.\\.\\.",  # Ellipsis (Protocol stubs)
]

exclude_also = [
    # Exclude entire files matching patterns
]

# Run unit tests
pytest tests/unit/ --cov=myapp --cov-report= --cov-append

# Run integration tests (appends to existing .coverage)
pytest tests/integration/ --cov=myapp --cov-report= --cov-append

# Generate combined report
coverage report --show-missing
coverage html

pip install pytest-cov coverage-enable-subprocess

# .coveragerc
[run]
concurrency = multiprocessing  # or 'thread' for threading-based parallelism
parallel = True

coverage combine    # Merge parallel .coverage.* files
coverage report
coverage html

# .coveragerc
[run]
source = .
omit =
    */migrations/*
    manage.py
    */wsgi.py
    */asgi.py
    */settings*.py
    */urls.py  # Often no logic to test

# Run Django tests with coverage
coverage run manage.py test
coverage report

# Or with pytest-django
pytest --cov=myapp --cov-report=html tests/

name: Tests with Coverage

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: '3.11'

      - name: Install dependencies
        run: pip install -r requirements-dev.txt

      - name: Run tests with coverage
        run: |
          pytest \
            --cov=myapp \
            --cov-branch \
            --cov-report=xml \
            --cov-report=html \
            --cov-fail-under=80 \
            tests/

      - name: Upload coverage to Codecov
        uses: codecov/codecov-action@v4
        if: always()
        with:
          file: coverage.xml
          token: ${{ secrets.CODECOV_TOKEN }}
          fail_ci_if_error: false

      - name: Upload HTML report
        uses: actions/upload-artifact@v4
        if: always()
        with:
          name: coverage-report
          path: htmlcov/

[![codecov](https://codecov.io/gh/yourorg/yourrepo/branch/main/graph/badge.svg)](https://codecov.io/gh/yourorg/yourrepo)

pip install coverage-badge
coverage-badge -o coverage.svg