Abstract
It is a continuous struggle to understand how much a product should be tested before the delivery to the market. Ericsson decided to evaluate the adequacy of unit test coverage criterion that they employed for years as a guide for sufficiency of testing. Naturally, if increasing coverage decreases the number of defects significantly, then coverage measures can be considered as criteria for test sufficiency. To test this hypothesis in practice, we investigated the relationship of unit test coverage measures and post-unit-test defects in a large commercial product of Ericsson. The results indicate that the sheer fulfillment of coverage does not seem to be any tangible help in producing defect-free software.