@Test
public void reduceWhenTargetWordIsFound() throws IOException, InterruptedException {

    Text key = new Text(WordReducer.TARGET_WORD);
    Iterable<IntWritable> values = createValues(1, 1, 1);
    reducer.reduce(key, values, contextMock);

    ArgumentCaptor<IntWritable> countArgument = ArgumentCaptor.forClass(IntWritable.class);

    verify(contextMock, times(1)).write(eq(key), countArgument.capture());
    verifyNoMoreInteractions(contextMock);

    IntWritable count = countArgument.getValue();
    assertEquals(3, count.get());
}