How do unit, module, and integration testing differ from each other?

Unit testing — is the verification of the smallest part of the code, usually a separate function or method, isolated from the rest of the system. The goal is to ensure that a specific block works correctly.

Module testing is often used as a synonym for unit testing, but sometimes module testing refers to testing a larger component — for example, a class or a module that may include several functions.

Integration testing checks the interaction between multiple modules or system components to ensure they work together correctly. For example, testing how two classes exchange data or how a service interacts with a database.

In summary:

• Unit/module testing — isolated verification of small parts of code.
• Integration testing — verification of interaction between components.