a system and method are disclosed for determining the root cause of non - deterministic tests . an exemplary system may receive a non - deterministic test and run the non - deterministic test with call trace collection enabled . for each trace , the system may determine whether the trace was associated with a passing or failing test . each trace may be labeled according to the trace &# 39 ; s association . then , dynamic call trees may be constructed , one for the traces associated with passing tests and one for traces associated with failing tests . the dynamic call trees may be compared to determine subtree patterns that occur in one tree , but not the other . the subtree patterns may then be ranked based on the number of times the subtrees occur in the traces in order to determine the root cause of the non - deterministic test .