All tests pass for combined birthday rulse with loyalty rules

Author: ardalis

DesignPatternsInCSharp/RulesEngine/Discounts/DiscountCalculate_CalculateDiscountPercentage.cs

@@ -62,14 +62,33 @@ public void Returns10PctForCustomersWhoAreVeterans(int customerAge)
         [InlineData(15, .15)]
         public void ReturnsCorrectLoyaltyDiscountForLongtimeCustomers(int yearsAsCustomer, decimal expectedDiscount)
         {
-            var customer = CreateCustomer(DEFAULT_AGE, 
+            var customer = CreateCustomer(DEFAULT_AGE,
                 DateTime.Today.AddYears(-yearsAsCustomer).AddDays(-1));
 
             var result = _calculator.CalculateDiscountPercentage(customer);
 
             result.Should().Be(expectedDiscount);
         }
 
+        [Theory]
+        [InlineData(1, .15)]
+        [InlineData(2, .18)]
+        [InlineData(5, .20)]
+        [InlineData(10, .22)]
+        [InlineData(15, .25)]
+        public void ReturnsCorrectLoyaltyDiscountForLongtimeCustomersOnTheirBirthday(int yearsAsCustomer, decimal expectedDiscount)
+        {
+            var customer = new Customer
+            {
+                DateOfBirth = DateTime.Today.AddYears(-DEFAULT_AGE),
+                DateOfFirstPurchase = DateTime.Today.AddYears(-yearsAsCustomer).AddDays(-1)
+            };
+
+            var result = _calculator.CalculateDiscountPercentage(customer);
+
+            result.Should().Be(expectedDiscount);
+        }
+
         [Theory]
         [InlineData(1)]
         [InlineData(2)]

DesignPatternsInCSharp/RulesEngine/Discounts/DiscountCalculator.cs

@@ -6,47 +6,56 @@ public class DiscountCalculator
     {
         public decimal CalculateDiscountPercentage(Customer customer)
         {
-            if(!customer.DateOfFirstPurchase.HasValue)
+            bool isBirthday = customer.DateOfBirth.HasValue && customer.DateOfBirth.Value.Month == DateTime.Today.Month && customer.DateOfBirth.Value.Day == DateTime.Today.Day;
+            if (!customer.DateOfFirstPurchase.HasValue)
             {
                 return .15m;
             }
             else
             {
                 if (customer.DateOfFirstPurchase.Value < DateTime.Now.AddYears(-15))
                 {
+                    if (isBirthday) return .25m;
                     return .15m;
                 }
                 if (customer.DateOfFirstPurchase.Value < DateTime.Now.AddYears(-10))
                 {
+                    if (isBirthday) return .22m;
                     return .12m;
                 }
-                if (customer.DateOfFirstPurchase.Value < DateTime.Now.AddYears(-5) ||
-                    (customer.DateOfBirth.HasValue && customer.DateOfBirth.Value.Month == DateTime.Today.Month && customer.DateOfBirth.Value.Day == DateTime.Today.Day))
+                if (customer.DateOfFirstPurchase.Value < DateTime.Now.AddYears(-5))
                 {
+                    if (isBirthday) return .20m;
                     return .10m;
                 }
                 if (customer.DateOfFirstPurchase.Value < DateTime.Now.AddYears(-2) &&
                     !customer.IsVeteran)
                 {
+                    if (isBirthday) return .18m;
                     return .08m;
                 }
                 if (customer.DateOfFirstPurchase.Value < DateTime.Now.AddYears(-1) &&
                     !customer.IsVeteran)
                 {
+                    if (isBirthday) return .15m;
                     return .05m;
                 }
             }
 
             if (customer.IsVeteran)
             {
+                if (isBirthday) return .20m;
                 return .10m;
             }
 
             if(customer.DateOfBirth < DateTime.Now.AddYears(-65))
             {
+                if (isBirthday) return .15m;
                 return .05m;
             }
 
+            if (isBirthday) return .10m;
+
             return 0;
         }
     }