Testing Principals

Principle 1 - Testing shows presence of defects

Testing can show that defects are present, but cannot prove that there are no defects.

Principle 2 - Exhaustive testing is impossible
Testing everything (all combinations of inputs and preconditions) is not feasible except for trivial cases.

Principle 3 - Early testing
Testing activities should start as early as possible in the SDLC.

Principle 4 - Defect clustering
A small number of modules contain most of the defects discovered during pre-release testing.


Principle 5 - Pesticide paradox
The test cases need to be regularly reviewed and revised

Principle 6 - Testing is context dependent

Testing is done differently in different contexts (safety-critical software is tested differently from e-commerce site)

Principle 7 - Absence-of errors fallacy

Finding and fixing defects does not help if the system built is unusable and does not fulfill the users' need and expectations.