Unit Testing glossary

28 Unit Testing terms, from Novice to Master. Start with the basics or jump to a level.

Updated October 16, 2026

Novice

Arrange, Act, Assert: Set up, do the action, check the result.
Assertion: A check that a result matches what you expect.
Passing and Failing Tests: Green means expected behaviour; red shows what broke.
Test Case: One specific scenario being checked.
Test Runner: The tool that finds, runs and reports tests.
Unit Test: A small automated check of one piece of code.

End-to-End Test: Tests the whole app like a user, often in a browser.
Integration Test: Checks that several parts work together for real.
Test Pyramid: Many unit tests, fewer integration tests, few end-to-end tests.
Test-Driven Development: Write a failing test first, then the code to pass it.

Code Coverage: How much code the tests execute.
Mock: A stand-in that records how it was called.
Red, Green, Refactor: The TDD loop: fail, pass, then tidy.
Setup and Teardown: Code run before and after each test.
Snapshot Testing: Save output at the beginning of a test, then check again later to see if the values changed.
Stub and Fake: Stubs return canned answers; fakes are simple working versions.
Test Double: Any stand-in object used in a test.
Test Naming: Names that state behaviour, condition and expected outcome.