public void IsNoVolumeContract()
        {
            var contract = ContractReaderStub.Contract();
            var volumes  = ContractProductSiteVolumeReaderStub.NoVolumes();
            var allSiteVolumesForTheContract =
                SiteVolumeCalculator.SiteVolumesForContract(contract,
                                                            volumes);

            var result =
                SiteVolumeCalculator.IsNoVolumeContract(allSiteVolumesForTheContract);

            Assert.AreEqual(true, result);
        }
        public void MissingBillingMonths()
        {
            var contract = ContractReaderStub.Contract();
            var volumes  = ContractProductSiteVolumeReaderStub.NoVolumes();

            var expectedBillingMonths =
                SiteVolumeCalculator.ExpectedBillingMonthsForTheContract(contract);
            var actualBillingMonths = SiteVolumeCalculator.BillingMonths(volumes);

            var missingBillingMonths =
                SiteVolumeCalculator.MissingBillingMonths(
                    expectedBillingMonths, actualBillingMonths);

            Assert.AreEqual(2, missingBillingMonths);
        }