Computerized testing of an object to identify one or more call sequences that give rise to exceptions. A set of potential operations (consisting of methods and associated parameter values) is automatically generated. A parameter generator may supply interesting parameter values that may more likely result in a thrown exception. A number of call sequences is automatically constructed using the operations in the set of operations as steps in the sequence. Each call sequence is then executed using a new instance of the object. If an exception is thrown, a report may be issued containing information helpful in evaluating whether the exception is appropriate. This information might include the exception type as well as the invalid call sequence that gave rise to the thrown exception. The invalid call sequence may also be minimized to assist the tester in evaluating the root cause and appropriateness of the exception.