What is the normal order of activities in which traditional software testing is organised?
1. Integration Testing
2. System Testing
3. Unit Testing
4. Validation Testing

Explanation

Conventional testing follows a spiral that widens outwards from the smallest unit of code to the complete system in its environment. It starts with unit testing (3) of individual modules, then integration testing (1) of the assembled modules, then validation testing (4) which checks the software against the customer's requirements, and finally system testing (2) where the validated software is exercised together with hardware, people and databases. That gives the order 3, 1, 4, 2. The other sequences either test the whole system before its parts or place validation after system testing, which reverses Pressman's standard testing strategy.