Unit testing: This involves testing individual components or units of the software to ensure they function correctly. In my experience, developers usually perform this type of testing.
Integration testing: This focuses on the interactions between different components of the software. I've found that this is important to ensure that the components work together as intended.
System testing: This is a high-level testing that validates the complete and integrated software system. From what I've seen, this helps ensure that the software meets the specified requirements and works as a whole.
Acceptance testing: This type of testing is done by the end users or clients to make sure the software meets their needs and expectations. A useful analogy I like to remember is that it's like a final "seal of approval" before the software is released.
Performance testing: This focuses on evaluating the software's performance under various conditions, such as load or stress. In my experience, this is crucial for ensuring that the software can handle real-world usage scenarios.
Security testing: This involves identifying potential vulnerabilities and weaknesses in the software to ensure that it is secure from unauthorized access and attacks. I've found that this is especially important for applications that handle sensitive data.