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

    LongWritable key = new LongWritable(1);
    mapper.map(key, new Text("I,"), contextMock);
    ArgumentCaptor<Text> keyArgument = ArgumentCaptor.forClass(Text.class);
    ArgumentCaptor<IntWritable> valueArgument = ArgumentCaptor.forClass(IntWritable.class);
    verify(contextMock, times(1)).write(keyArgument.capture(), valueArgument.capture());
    assertEquals("I", keyArgument.getValue().toString());
    assertEquals(1, valueArgument.getValue().get());
    verifyNoMoreInteractions(contextMock);
}