Unit Testing Best Practices for JavaScript

Unit tests verify individual pieces of code work correctly. Well-written tests catch bugs early and serve as documentation. Here's how to write tests that provide real value.

Test Structure (AAA Pattern)#

Naming Conventions#

Testing Pure Functions#

Mocking Dependencies#

Testing Async Code#

Test Data Factories#

What Not to Test#

Code Coverage Guidelines#

Conclusion#

Good unit tests are fast, isolated, and focused on behavior. They catch bugs, enable refactoring, and document intent.

Write tests that you'd want to maintain—clear, purposeful, and valuable.