TestFixture

A test fixture, in software testing, is a fixed state of a set of objects or resources used as a baseline for running tests. Fixtures prepare the environment so that tests are repeatable and isolated. They commonly include test data, configuration, and resources such as database tables, files, or network connections, and they may be created programmatically or loaded from external sources. The term is commonly written as "test fixture," though some sources use the single-word form testfixture.

Fixtures establish the preconditions for a test. They are typically set up before a test runs and torn down afterward, ensuring that tests do not depend on the results of others. The scope can be per-test, meaning a fresh fixture is created for each test, or per-suite, where a shared fixture is created once for a group of tests.

Types of fixtures include data fixtures, which seed a database with known records; environment or configuration fixtures, which prepare system settings; and resource fixtures, which allocate files, sockets, or external services needed by tests. When describing data fixtures, a common example is a user record with fields such as id, name, and email used by several tests.

Fixtures can be managed in several ways. Some frameworks ship with built-in fixture files (for example, YAML or JSON data files) that are loaded before tests. Others rely on factory or fixture libraries to create objects on demand. In unit tests, fixtures are often created in setup methods; in parameterized tests, fixtures can be varied across runs.

Good fixture design emphasizes minimalism, isolation, and maintainability. Overly large or coupled fixtures can make tests fragile; using factories or helpers and rolling back changes between tests can help. Documentation and version control of fixture data are common best practices.