Unit testing is performed by the to verify that individual units of source code are working as expected.

9. is performed to verify the interaction between different software modules.

System testing is performed on a complete, integrated system to evaluate the system's with its specified requirements.

3. testing is also known as structural testing or glass-box testing.

In beta testing, the software is tested by a group of potential users in a environment.

The purpose of system testing is to ensure that all system components work together as .

In , developers review the program code to find defects and suggest improvements.