A MochaJS developer designs, builds, and maintains JavaScript applications using MochaJS, a feature-rich JavaScript test framework. They write server-side, client-side, and API tests to ensure the functionality and reliability of the software. They are responsible for implementing test-driven development methodologies, utilizing MochaJS for unit and integration testing. They also debug and fix issues identified during testing, and collaborate with other developers to integrate new features and optimize code. Their goal is to deliver high-quality, error-free software products by incorporating MochaJS into the development and testing processes. They also keep themselves updated with the latest MochaJS updates and improvements.