Exception raised when a test failed, with the list of counter-examples. Test_fail (name, l) means test name failed on elements of l.

Exception raised when a test raised an exception e, with the sample that triggered the exception. Test_error (name, i, e, st) means name failed on i with exception e, and st is the stacktrace (if enabled) or an empty string.

Exception raised when a negative test failed. Test_unexpected_success name means test name failed to find an expected counter example.