Testing shows presence of defects: Testing identifies the defects, Flows and errors present in the software but cannot prove that software is 100% defect free.

Exhaustive Testing is impossible: It is not possible to test every combination of inputs and preconditions.

Early testing: The testing activities should start early in the stage of SDLC.

Defect Clustering: A small Number of modules contain most of the defect discovered during pre-release testing.

Pesticide paradox: When the same kind of testing repeated again and again, eventually same test cases set no longer able to find the any new bug.

Testing is context depending: Testing process is context dependent. Different Kinds of site are tested differently.

Absence-of-errors fallacy: Finding and fixing of bug is not help full when built is unusable or dont fulfill the users need.