What is the typical order of testing levels?

The typical order of testing levels starts with unit testing, which focuses on individual components or functions of the software. This is the initial phase where developers test the smallest parts of the application in isolation to verify that each unit works as intended.

Following unit testing is system testing, a more comprehensive level where the entire software application is tested as a complete and integrated system. This phase evaluates the overall behavior and performance of the system against the specified requirements, ensuring that all components work together seamlessly.

Acceptance testing comes next, which is usually conducted to determine whether the system meets the acceptance criteria set by stakeholders. This level of testing involves end-users or stakeholders testing the system in the real-world scenario to ensure it meets their needs and requirements.

Maintenance testing is typically done after the software is deployed and addresses any issues that arise post-release. This phase may involve testing updates, bug fixes, or alterations to ensure that the existing functionalities still perform correctly and that new changes do not introduce new issues.

This progression reflects a logical and structured approach to testing where each level builds upon the previous one, ensuring that each aspect of the software is thoroughly vetted before it reaches the final user, highlighting the importance of each testing level in delivering a reliable and functional product.