What is unit testing answer?
In a professional tone: If you’re writing code for the web, it’s important to understand the concept of unit testing. Unit testing is a way to ensure that the code you’ve written works as intended, and can also be used to ensure you didn’t introduce any bugs or break existing functionality as you were making changes. When automated tests are run against a website, they ensure that the site’s code still functions. If a test fails, it gives an indication that some part of the site isn’t working as expected—and it allows developers to fix it quickly.
Learn more: What is Unit Testing? Definition from WhatIs.com