@Test
  public void testRequestedSizeWithinGraceHeadroomSeverity() {
    testHelper(
        ImmutableMap.of(Constants.WORKER_JOB_NAME, new double[]{
            1.5e9,
            1.6e9,
        }),
        ImmutableMap.of(Constants.WORKER_JOB_NAME, "3g"),
        Severity.NONE,
        0
    );
  }
Though memory utilization is about 50%, severity should be none
because requested memory is within the default 2 GB grace headroom of the
max used memory.
test/com/linkedin/drelephant/tony/heuristics/TaskMemoryHeuristicTest.java