# 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](https://www.ask-codey.com/glossary/arrange-act-assert): Set up, do the action, check the result.
- [Assertion](https://www.ask-codey.com/glossary/assertion-unit-testing): A check that a result matches what you expect.
- [Passing and Failing Tests](https://www.ask-codey.com/glossary/passing-and-failing-tests): Green means expected behaviour; red shows what broke.
- [Test Case](https://www.ask-codey.com/glossary/test-case): One specific scenario being checked.
- [Test Runner](https://www.ask-codey.com/glossary/test-runner): The tool that finds, runs and reports tests.
- [Unit Test](https://www.ask-codey.com/glossary/unit-test-unit-testing): A small automated check of one piece of code.

## Apprentice

- [End-to-End Test](https://www.ask-codey.com/glossary/end-to-end-test): Tests the whole app like a user, often in a browser.
- [Integration Test](https://www.ask-codey.com/glossary/integration-test): Checks that several parts work together for real.
- [Test Pyramid](https://www.ask-codey.com/glossary/test-pyramid): Many unit tests, fewer integration tests, few end-to-end tests.
- [Test-Driven Development](https://www.ask-codey.com/glossary/test-driven-development): Write a failing test first, then the code to pass it.

## Journeyman

- [Code Coverage](https://www.ask-codey.com/glossary/code-coverage): How much code the tests execute.
- [Mock](https://www.ask-codey.com/glossary/mock): A stand-in that records how it was called.
- [Red, Green, Refactor](https://www.ask-codey.com/glossary/red-green-refactor): The TDD loop: fail, pass, then tidy.
- [Setup and Teardown](https://www.ask-codey.com/glossary/setup-and-teardown): Code run before and after each test.
- [Snapshot Testing](https://www.ask-codey.com/glossary/snapshot-testing): Save output at the beginning of a test, then check again later to see if the values changed.
- [Stub and Fake](https://www.ask-codey.com/glossary/stub-and-fake): Stubs return canned answers; fakes are simple working versions.
- [Test Double](https://www.ask-codey.com/glossary/test-double): Any stand-in object used in a test.
- [Test Naming](https://www.ask-codey.com/glossary/test-naming): Names that state behaviour, condition and expected outcome.

## Freelancer

- [Contract Test](https://www.ask-codey.com/glossary/contract-test): Checks a service still matches its agreed contract.
- [Flaky Test](https://www.ask-codey.com/glossary/flaky-test): A test that passes or fails at random.
- [Locator](https://www.ask-codey.com/glossary/locator): A way to find elements by role, label or text.
- [Playwright](https://www.ask-codey.com/glossary/playwright): A tool for automated end-to-end browser tests.
- [Property-Based Testing](https://www.ask-codey.com/glossary/property-based-testing): Checking a rule against many generated inputs.
- [Test Isolation](https://www.ask-codey.com/glossary/test-isolation): Each test stands alone, independent of others.
- [Testcontainers](https://www.ask-codey.com/glossary/testcontainers-unit-testing): Real databases in throwaway Docker containers for tests.

## Master

- [Approval Testing](https://www.ask-codey.com/glossary/approval-testing): Comparing output against an approved file.
- [Characterization Test](https://www.ask-codey.com/glossary/characterization-test): A test recording what existing code does today.
- [Mutation Testing](https://www.ask-codey.com/glossary/mutation-testing): Deliberately breaking code to check tests notice.

[More subjects in Programming Fundamentals](https://www.ask-codey.com/glossary/groups/programming-fundamentals)

Source: https://www.ask-codey.com/glossary/subjects/unit-testing