Question

Why is it necessary to test a large program at three different levels: unit, integration as well as system level rather than thoroughly testing only at the system level

Answer 1

Each type of this has unique features and the thought is to eliminate the issues at each stage itself before release to customer.

Explanation:

• The application is submitted during unit testing to evaluations focusing on specific units or elements of the software to evaluate if each one is fully functional.
• Integration testing allows the opportunity to combine all of the units within a program and test them as a group. This level of testing is optimized for detecting interface faults between the modules / functions.
• System testing is the first level where the whole application is tested in its entirety. At this level, the goal is to assess whether the system has met all of the requirements outlined and to see that it meets the quality standards.