### Question:
GraphqlClientDataSourceServlet extends SlingSafeMethodsServlet { @Reference( service = GraphqlClient.class, bind = "bindGraphqlClient", unbind = "unbindGraphqlClient", cardinality = ReferenceCardinality.MULTIPLE, policy = ReferencePolicy.DYNAMIC) void bindGraphqlClient(GraphqlClient graphqlClient, Map<?, ?> properties) { identifiers.add(graphqlClient.getIdentifier()); }   final static String RESOURCE_TYPE; }### Answer:
@Test public void testBindGraphqlClient() { GraphqlClient mockClient = mock(GraphqlClient.class); Mockito.doReturn("my-identifier").when(mockClient).getIdentifier(); servlet.bindGraphqlClient(mockClient, Collections.emptyMap()); Set<String> identifiers = (Set<String>) Whitebox.getInternalState(servlet, "identifiers"); Assert.assertEquals(1, identifiers.size()); Assert.assertTrue(identifiers.contains("my-identifier")); }