### Question:
StatisticsServiceImpl implements StatisticsService { @Override @CatAnnotation public List<DataPoint> findByAccountName(String accountName) { Assert.hasLength(accountName); return repository.findByIdAccount(accountName); }  @Override @CatAnnotation List<DataPoint> findByAccountName(String accountName); @Override @CatAnnotation DataPoint save(String accountName, Account account);  }### Answer:
@Test public void shouldFindDataPointListByAccountName() { final List<DataPoint> list = ImmutableList.of(new DataPoint()); when(repository.findByIdAccount("test")).thenReturn(list); List<DataPoint> result = statisticsService.findByAccountName("test"); assertEquals(list, result); }
@Test(expected = IllegalArgumentException.class) public void shouldFailToFindDataPointWhenAccountNameIsNull() { statisticsService.findByAccountName(null); }
@Test(expected = IllegalArgumentException.class) public void shouldFailToFindDataPointWhenAccountNameIsEmpty() { statisticsService.findByAccountName(""); }