Levels of Testing

There are 5 levels of testing. They are as follows.

1. Component/Unit testing
2. Integration testing
3. System testing
4. Acceptance testing
5. Regression testing

Component/Unit Testing:

Testing of individual component is called as component testing.

Integration Testing:

Testing the components together to find out how they behave with each other. Here the focus is on the interface. There are several instances where the individual components would be working fine, but when all the components get integrated, they don't work. So integration testing has lot of importance.

System Testing:

Testing the functionality of a system with the intent of identifying defects is called as System Testing. Here the testing usually focuses either/or two documents. 1) Specifications 2) Use Cases. Some times non-functional testing also becomes part of system testing. This basically depends on the SLAs.

Acceptance Testing:

Here usually the customer gets involved. But sometimes, the customer suggests the organization to keep a team in stead of he being involved in the testing. Here the application is tested against the defined acceptance criteria in the contract

Regression Testing:

Software applications are subjected to change. There are many examples where new change in the system have introduced several defects and/or affected the old functionality. So the dependent functionality(s) should be tested whenever a change is introduced in the system. The regression test(s) should be automated to reduce time in testing the same scenarios multiple times.