Unit testing is a crucial aspect of software development that involves dividing application code into units and writing tests for each unit to ensure it meets its design and behaves as intended. Developers often write unit tests alongside their source code, leveraging testing libraries to automate test execution during development. These tests can be executed as part of a CI/CD pipeline, helping prevent bugs from entering production code. Unit tests focus on the low-level functionality of the code, but what if you need to test that the code works together? In such cases, integration and functional testing come into play, which combine individual software modules to fulfill higher-level requirements. Regression testing ensures existing features are not broken by new features. Various testing frameworks, including Test-Driven Development (TDD) and Behavior-Driven Development (BDD), provide strategies for better testing and collaboration. Examples of unit testing can be seen in ReactJS and Python applications, highlighting the importance of writing tests to ensure code quality and reliability. While unit testing is not a one-size-fits-all practice, exploring options and best practices can help developers fit them into their application.