@Test
  public void testGlobalMapping() throws Exception {
    ServiceInfo sinfo = metaInfo.getService("HDP",
        "0.2", "HDFS");
    List<PropertyInfo> pinfo = sinfo.getProperties();
    // check all the config knobs and make sure the global one is there
    boolean checkforglobal = false;

    for (PropertyInfo pinfol: pinfo) {
      if ("global.xml".equals(pinfol.getFilename())) {
        checkforglobal = true;
      }
    }
    Assert.assertTrue(checkforglobal);
    sinfo = metaInfo.getService("HDP",
        "0.2", "MAPREDUCE");
    boolean checkforhadoopheapsize = false;
    pinfo = sinfo.getProperties();
    for (PropertyInfo pinfol: pinfo) {
      if ("global.xml".equals(pinfol.getFilename())) {
        if ("hadoop_heapsize".equals(pinfol.getName())) {
          checkforhadoopheapsize = true;
        }
      }
    }
    Assert.assertTrue(checkforhadoopheapsize);
  }
Make sure global mapping is avaliable when global.xml is
in the path.
ambari-server/src/test/java/org/apache/ambari/server/api/services/AmbariMetaInfoTest.java