I am writing some test code for a processElement function in Apache Flink 1.4:
public class ProcessFunctionClass {
public void processElement(Tuple2<String, String> tuple2, Context context, Collector<Tuple2<String, String>> collector) {
// if the state is empty, start a timer
if (listState.get().iterator().hasNext() == false)
context.timerService().registerEventTimeTimer(1000);
listState.add("someStringToBeStored");
// ...
}
}
public class ProcessFunctionClassTest {
private ProcessFunctionClass processFunctionClass;
@Mock
private ListState<String> listState;
@Before
public void setUp() throws Exception {
processFunctionClass = new ProcessFunctionClass();
}
@Test
public void testProcessElement() {
ListState mockListState = mock(ListState.class);
Iterable mockIterable = mock(Iterable.class);
Iterator mockIterator = mock(Iterator.class);
MockitoAnnotations.initMocks(this);
when(tDPListState.get()).thenReturn(mockIterable);
when(tDPListState.get().iterator()).thenReturn(mockIterator);
when(tDPListState.get().iterator().hasNext()).thenReturn(false);
processFunctionClass.processElement(tuple2, context, collector);
// verify(...)
}
}
When I debug using my IDE, just before I step into the processElement() method, listState is not null and appears to have been mocked successfully, but as soon as I get to listState.get().iterator().hasNext(), listState is null and I get a NullPointerException. What am I doing wrong here?
In ProcessFunctionClass you have a private listState variable. In your test you create a completely unrelated mockListState variable and set some expectations on it.
For your test to work, you must provide a way (constructor or setter) to set ProcessFunctionClass.listState to desired value (your mocked list state)
On top of that, MockitoAnnotations.initMocks(this); seems to do nothing in your example: you haven't shown us any fields annotated with @Mock or @InjectMocks
Update
You are misusing @Mock annotation. You should place it in the test class, not in class under test. When placed in the test class, after a call to initMocks, the filed will be initialized with a mock of an appropriate type.
What you should fo instead:
MockitoAnnotations.initMocks(this);, you are creating all the mocks manually.ProcessFunctionClasspublic ProcessFunctionClass(ListState<String> listState) {
this.listState = listState
}
var mockListState = mock(ListState.class);
var processFunctionClass = new ProcessFunctionClass();
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