Coverage.py vs Coveralls

Coverage.py measures which parts of Python programs run and highlights executable code that remains untouched, helping developers assess what their tests exercise. It measures statement coverage by default and can also track branch coverage. Reports are available as text, HTML, XML, LCOV, and JSON. Dynamic contexts can associate lines of execution with the test function that ran them. Coverage.py can run test suites through their usual command; pytest-cov is available but the documentation says most users do not need it. Third-party plugins can extend measurement to non-Python files, such as connecting executed Python to Django templates. Data is stored in a SQLite database, and advanced use can rely on its API. The current documentation lists Python 3.10 through 3.15 rc2 and PyPy3 versions 3.10 and 3.11. The tool provides ctrace, pytrace, and sysmon measurement cores; sysmon is faster for simple line and branch coverage but lacks support for dynamic contexts and plugins. Coverage.py is licensed under Apache 2.0 and runs on Linux, macOS, and Windows, with self-hosting available. It is free.

Coveralls analyzes software test coverage, showing teams which code is not covered by tests. Its dashboard presents project coverage percentages and their changes over time, while repository views drill down from a project to sub-projects, files, and individual lines. Build history tracks coverage across branches, including pull requests. Coveralls can add summarized coverage results to pull requests and send status updates that apply coverage criteria to merge decisions. Notifications can go to Slack or webhooks. It supports line and branch coverage, with report formats including LCOV, SimpleCov, Cobertura, JaCoCo, and Clover XML. Coveralls says it works with any CI service and lists more than 30 community-created integrations, a GitHub Action, and a CircleCI Orb. An API can add repositories programmatically and return recent build statistics. Open-source and public repositories are free. The Starter plan is $10 a month for one private repository and includes a 30-day trial. A self-hosted enterprise installation can operate within existing security controls without outbound network access.