Unit testing
software testing method by which individual units of source code are validated
Unit testing, also known as component or module testing, is a form of software testing by which isolated source code is tested to validate expected behavior.
Unit testing describes tests that are run at the unit-level to contrast testing at the integration or system level.
History
Unit testing, as a principle for testing separately smaller parts of large software systems, dates back to the early days of software engineering. In June 1956 at US Navy's Symposium on Advanced Programming Methods for Digital Computers, H.D. Benington presented the SAGE project. It featured a specification-based approach where the coding phase was followed by "parameter testing" to validate component subprograms against their specification, followed then by an "assembly testing" for parts put together.
In 1964, a similar approach is described for the software of the Mercury project, where individual units developed by different programmers underwent "unit tests" before being integrated together. In 1969, testing methodologies appear more structured, with unit tests, component tests and integration tests collectively validating individual parts written separately and their progressive assembly into larger blocks. Some public standards adopted in the late 1960s, such as MIL-STD-483 and MIL-STD-490, contributed further to a wide acceptance of unit testing in large projects.
Unit testing was in those times interactive or automated, using either coded tests or capture and replay testing tools. In 1989, Kent Beck described a testing framework for Smalltalk (later called SUnit) in "Simple Smalltalk Testing: With Patterns".
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The subject matters to the science & nature register because the source frames it as software testing method by which individual units of source code are validated. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated Aug 20, 2026. The linked authority identifier is Q907375. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1956, 1964, 1969 and 1989.
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This entry incorporates text from “Unit testing” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.