@Test
  public void testRegisterAndFetchObject() {
    String value = "hello world";
    internalTaskContext.registerObject("key", value);
    assertEquals(value, internalTaskContext.fetchObject("key"));
    assertNull(internalTaskContext.fetchObject("not a key"));
  }
Given a registered object, fetchObject should get it. If an object is not registered at a key, then fetchObject
should return null.
samza-core/src/test/java/org/apache/samza/context/TestInternalTaskContext.java