A Thousand Tests equals Zero Coverage

That title was indeed intended to draw your attention !

However, the title is not far from the truth. We often hear testing teams claim test coverage numbers that are closer to 100 per cent. The same numbers may be looked at as equaling zero coverage. It all depends on what you base your measurement of test coverage. This is something most folks in testing realize.

If test coverage is measured as a percentage of all the tests that could be run for a regular real world enterprise application, the coverage number would be near or equal to zero. It does not matter if you have executed a thousand or more tests for the application. This is due to the fact that the number of possible tests you could execute is almost infinite.

Since a true hundred percent of testing of the application is neither feasible nor possible, the testing team has to make intelligent choices of subsets of tests to be executed. This subset would normally target the areas that are at higher risk levels (likelihood and impact) and represent most value for the stakeholders.