Inputs to a system under test (SUT) are modeled as a collection of attribute-value pairs. A set of testcases is executed using an initial set of test vectors that provides complete n-wise coverage of the attribute-value pairs. For each execution of the testcases, for each attribute-value pair, a non-binary success rate (SAV) is computed based on the binary execution results. in response to a success rate of an attribute-value pair being below a predetermined threshold, a subset of testcases that use the attribute-value pair is identified. Further, sets of code paths for the subset of testcases are identified, each set of code path respectively corresponding to a testcase from the subset of testcases. Further, an intersection of the sets of code paths is determined. Code paths of the SUT that are in the intersection, are highlighted to represent a soft failure with the SUT.