public void TestGetListOfCustomersWithBirthdayToday()
        {
            var customerManagerMock = new Mock <ICustomerManager>();

            customerManagerMock.Setup(m =>
                                      m.GetAllCustomers())
            .Returns(new List <Customer>
            {
                new Customer {
                    DateOfBirth = new DateTime(2000, DateTime.Today.Month, DateTime.Today.Day)
                },
                new Customer {
                    DateOfBirth = new DateTime(2018, 8, 9)
                }
            });

            var customerAPI = new CustomerAPI(customerManagerMock.Object, null, null);
            var result      = customerAPI.GetListOfCustomersWithBirthdayToday();

            Assert.AreEqual(1, result.Count());
        }