@Test
  public void testGetInstance() {
    assertThat(CompatibilitySingletonFactory.getInstance(MetricsThriftServerSourceFactory.class),
      instanceOf(MetricsThriftServerSourceFactoryImpl.class));
  }
Test for the interface of MetricsThriftServerSourceFactory
hbase-hadoop-compat/src/test/java/org/apache/hadoop/hbase/thrift/TestMetricsThriftServerSourceFactory.java