### Question:
MRApps extends Apps { public static JobId toJobID(String jid) { Iterator<String> it = _split(jid).iterator(); return toJobID(JOB, jid, it); }  static String toString(JobId jid); static JobId toJobID(String jid); static JobId toJobID(String prefix, String s, Iterator<String> it); static String toString(TaskId tid); static TaskId toTaskID(String tid); static TaskId toTaskID(String prefix, String s, Iterator<String> it); static String toString(TaskAttemptId taid); static TaskAttemptId toTaskAttemptID(String taid); static String taskSymbol(TaskType type); static TaskType taskType(String symbol); static TaskAttemptStateUI taskAttemptState(String attemptStateStr); static void setInitialClasspath(
      Map<String, String> environment); static void addToClassPath(
      Map<String, String> environment, String fileName); static Path getStagingAreaDir(Configuration conf, String user); static String getJobFile(Configuration conf, String user, 
      org.apache.hadoop.mapreduce.JobID jobId); static final String JOB; static final String TASK; static final String ATTEMPT; static final String CLASSPATH; }### Answer:
@Test public void testToJobID() { JobId jid = MRApps.toJobID("job_1_1_1"); assertEquals(1, jid.getAppId().getClusterTimestamp()); assertEquals(1, jid.getAppId().getId()); assertEquals(1, jid.getId()); }
@Test(expected=YarnException.class) public void testJobIDShort() { MRApps.toJobID("job_0_0"); }