Unit Testing

What is Unit Testing?

Unit testing verifies the smallest testable parts of an application — individual functions, methods, or components — in isolation from the rest of the system.

Key Characteristics

• Typically performed by developers using automated frameworks (e.g., JUnit, NUnit, Jest).
• Executed frequently, often as part of continuous integration pipelines.
• Uses mocks and stubs to isolate the unit under test from its dependencies.
• Forms the base of the testing pyramid — fast, cheap, and high in number.

Benefits

Unit testing catches defects at the earliest and cheapest stage, makes refactoring safer, and serves as living documentation for how individual components are expected to behave.