There are four main testing stages in a structured software development process. They are:
Unit Testing
These tests demonstrate that a single program, module, or unit of code function as designed. For example, observing the result when pressing a function key to complete an action. Tested units are ready for testing with other system components such as other software units, hardware, documentation, or users.
Integration Testing
These tests are conducted on tasks that involve more than one application or database, or on related programs, modules, or units of code, to validate that multiple parts of the system interact according to the system design. Each integrated portion of the system is then ready for testing with other parts of the system.
System Testing
These tests simulate operation of the entire system and confirm that it runs correctly. Upon completion, the validated system requirements result in a tested system based on the specification developed or purchased.
User Acceptance Testing
This real-world test is the most important to the business, and it cannot be conducted in isolation. Internal staff, customers, vendor, or other users interact with the system to ensure that it will function as desired regardless of the system requirements. The result is a tested system based on user needs.
