BigtableConfig implements Serializable { BigtableConfig withInstanceId(ValueProvider<String> instanceId) { checkArgument(instanceId != null, "Instance Id of BigTable can not be null"); return toBuilder().setInstanceId(instanceId).build(); }  @Override String toString();  }
@Test public void testWithInstanceId() { assertEquals(INSTANCE_ID.get(), config.withInstanceId(INSTANCE_ID).getInstanceId().get()); thrown.expect(IllegalArgumentException.class); config.withInstanceId(null); }