### Question:
BillingApiService { public List<BillingChartInfo> getBillingChartInfo(final BillingChartRequest request) { return billingManager.getBillingChartInfo(request); }  List<BillingChartInfo> getBillingChartInfo(final BillingChartRequest request); List<BillingChartInfo> getBillingChartInfoPaginated(final BillingChartRequest request); List<String> getAllBillingCenters();  }### Answer:
@Test public void shouldReturnBillingChartInfoList() { when(mockBillingManager.getBillingChartInfo(billingChartRequest)).thenReturn(billingChartInfos); assertThat(billingApiService.getBillingChartInfo(billingChartRequest)).isEqualTo(billingChartInfos); }