unit test
An automated test that verifies the behaviour of a single, isolated unit of source code — typically a function or class method — independent of external systems.
Full Definition
Unit tests are the foundation of automated test suites, designed to validate individual functions or methods in isolation from databases, networks, and other external dependencies (which are replaced by mocks or stubs). They run quickly, provide precise failure attribution, and are typically written by developers alongside the code being tested. Editors must distinguish 'unit test' from 'integration test' (which tests interactions between components) and 'end-to-end test' (which simulates real user workflows). As a noun phrase, 'unit test' is two unhyphenated words; as a compound modifier, hyphenate: 'a unit-test framework'. The verb form is 'unit-test' (hyphenated): 'to unit-test a function'.
Usage
Usage note: Two words as a noun ('write a unit test'); hyphenate as a modifier ('unit-test coverage') or verb ('unit-test this module'). Do not confuse with 'integration test' or 'end-to-end test', which involve multiple components or full system flows.
In Context
- "Each unit test should cover a single code path and assert one specific outcome to keep failures easy to diagnose." — Testing best-practices guide
- "The project maintains 90% unit-test coverage, measured on every CI run." — Engineering quality report