Evaluating the efficiency of continuous testing during test-driven development

Continuous testing is a novel feature within modern programming environments, where unit tests constantly run in the background providing early feedback about breaking changes. One of the more challenging aspects of such a continuous testing tool is choosing the heuristic which selects the tests to run based on the changes recently applied. To help tool builders select the most appropriate test selection heuristic, we assess their efficiency in a continuous testing context. We observe on two small but representative cases that a continuous testing tool generates significant reductions in number of tests that need to be executed. Nevertheless, these heuristics sometimes result in false negatives, thus in rare occasions discard pertinent tests.