Unit testing and integration testing are two fundamental approaches in software development, each serving a distinct purpose to ensure reliable and functional software. Unit testing involves verifying individual components of a software application independently to ensure they function as intended, and is typically performed by developers during the development phase. This type of testing is fast and focuses on small, isolated units of code, like functions or methods, without relying on external software. Integration testing, on the other hand, is conducted after unit tests to validate the interactions between multiple components, ensuring they work seamlessly together. This approach is crucial for verifying data flow, APIs, and system interactions across various modules, often involving real or combined dependencies. While unit tests are fast and low-cost in terms of maintenance, integration tests are more complex, slower, and involve higher maintenance due to the multiple dependencies involved. Both testing methods are essential, with unit tests providing early error detection and integration tests ensuring the overall functionality of the application. Effective testing strategies often include a mix of both, optimizing for CI/CD pipelines through parallel execution, test prioritization, and automation to maintain high-quality standards throughout the software lifecycle.