Testtools

Testtools is a Python library that provides a collection of utilities to assist in writing unit tests. It is designed to be framework-agnostic, allowing test authors to use its components with unittest, pytest, or other frameworks. The project aims to provide small, composable building blocks that improve reliability and readability of tests without tying the code to a single test runner.

The library's core is a TestCase class (testtools.testcase.TestCase) that offers extended lifecycle management, cleanup handling, and helpers beyond the standard library's unittest. It also ships a suite of assertion helpers and matchers under testtools.matchers, enabling expressive checks such as type, value, and structure comparisons. Additional modules provide test doubles, temporary resource management, output capture, and facilities for testing asynchronous code and subprocess interactions. Together these utilities help reduce boilerplate in tests and enable more precise failure reporting.

Testtools is used in numerous Python projects and ecosystems, including large open-source deployments. It is distributed via PyPI and maintained as an independent package; it is designed to be importable and usable without forcing a particular test framework, though it is commonly used alongside unittest and pytest.

See also: unittest, pytest, assertion matchers, test doubles, open-source testing tools.