A method for testing a system under test (SUT) in an active environment includes generating, by a testing system, several tests for testing the SUT. The tests are generated based on a coverage model of the SUT, which includes multiple attributes. The method further includes creating, by the testing system, a minimal set of tests from the tests by selecting tests that do not exceed a predetermined performance threshold. The method further includes executing, by the testing system, the minimal set of tests on the SUT for analyzing a soft failure of the SUT in the active environment. The soft failure occurs in the active environment during execution of the SUT based at least in part on a performance parameter of the active environment.