### Question:
DocumentRegistry { @Nullable public SwaggerV2Documentation get(String serviceName) { return storage.get(serviceName); }  static DocumentRegistry getInstance(); void put(String serviceName, SwaggerV2Documentation swaggerV2Documentation); @Nullable SwaggerV2Documentation get(String serviceName);  }### Answer:
@Test public void get() { SwaggerV2Documentation swaggerV2Documentation = Mockito.mock(SwaggerV2Documentation.class); DocumentRegistry.getInstance().put("foo", swaggerV2Documentation); assertEquals(swaggerV2Documentation, DocumentRegistry.getInstance().get("foo")); }