Before launching an application, it is key to ensure that everything works well. This is where testing comes in, which is the process of evaluating software to detect errors, verify that it meets requirements, and guarantee that the user experience is optimal. There are different types of tests, such as unit tests (small parts of the code are tested), functional tests (verifying that everything does what it should), and performance tests (measuring how the system responds under different workloads). Good testing avoids problems in production and improves software quality.