8 best JavaScript Functional testin libraries in 2025

Functional testing is a type of software testing in which applications are tested for their intended functionality. It's also called black-box testing because the internal code isn't examined. Instead, testers look at the inputs and outputs of an application to see if they match up with what they're supposed to be. In order to use JavaScript in testing, you will need a browser or a browser automation tool. We will look at the 8 best JavaScript open-source functional testing libraries including cypress - Fast, easy, and reliable testing for anything that runs in a browser; enzyme - JavaScript Testing utilities for React; react-testing-library - Simple and complete React DOM testing utilities.