In reply to Subbi Reddy:
I agree with Jon, this is a very good interview questions. The interviewer was not looking for a solution, instead they’re looking for the process you would follow to find a solution. That would include isolating the test and eliminating other possible causes. Did the tests all run on the same machine with the same version of software? Did they run in parallel or sequentially? At what point did the test fail and how did it fail? Etc.