TestPipes invokes the main method of the program running pipes. In
MAPREDUCE-421, a change was made to the Pipes command runner to invoke System.exit after completion. This itself is a valid change because the pipes command runner is in itself a user facing program. But when combined with a testcase, it causes the testcase to crash rather than providing feedback on whether the test ran correctly or not.
The testcase should be modified to use Tool instead of running main directly.