Unit testing means testing the smallest parts of your code, such as individual functions or methods.
Instead of testing the whole application at once, unit testing focuses on one piece at a time to make sure it works correctly.
This approach helps developers catch bugs early and makes applications easier to maintain as they grow.
Why Unit Testing Matters
- Finds bugs at the earliest stage
- Makes code easier to change safely
- Improves confidence in development
- Reduces future debugging time
- Encourages clean and modular code
Professional developers rely heavily on unit tests.
This function returns the square of a number.
Now we will test it using simple unit tests.
The test checks only one function and one output.
This is the core idea of unit testing.
These examples show how unit testing focuses on small, clear checks.
By practicing unit testing, students gain the habit of validating each part of their code — a key step toward building reliable, maintainable, and professional JavaScript applications.