🔴 Add test for 0 subscriptions

Author: isaac1024

exercises/tiered_pricing/solutions/isaac1024_baby-steps/src/tiered_pricing.rs

@@ -1,16 +1,16 @@
-fn get_total_subscription_price(number_of_subscriptions: u32) -> u32 {
+fn get_total_subscription_price(number_of_subscriptions: u32) -> Result<u32, String> {
     const FIRST_UNIT_PRICE: u32 = 299;
     const SECOND_UNIT_PRICE: u32 = 239;
     const THIRD_UNIT_PRICE: u32 = 219;
     const FOURTH_UNIT_PRICE: u32 = 199;
     const FIFTH_UNIT_PRICE: u32 = 149;
 
     match number_of_subscriptions {
-        1|2 => FIRST_UNIT_PRICE * number_of_subscriptions,
-        3..=10 => SECOND_UNIT_PRICE * number_of_subscriptions,
-        11..=25 => THIRD_UNIT_PRICE * number_of_subscriptions,
-        26..=50 => FOURTH_UNIT_PRICE * number_of_subscriptions,
-        _ => FIFTH_UNIT_PRICE * number_of_subscriptions,
+        1|2 => Ok(FIRST_UNIT_PRICE * number_of_subscriptions),
+        3..=10 => Ok(SECOND_UNIT_PRICE * number_of_subscriptions),
+        11..=25 => Ok(THIRD_UNIT_PRICE * number_of_subscriptions),
+        26..=50 => Ok(FOURTH_UNIT_PRICE * number_of_subscriptions),
+        _ => Ok(FIFTH_UNIT_PRICE * number_of_subscriptions),
     }
 }
 
@@ -19,52 +19,67 @@ mod tests {
     use crate::tiered_pricing::get_total_subscription_price;
 
     #[test]
-    fn when_get_a_subscription_return_299_euros() {
-        assert_eq!(299, get_total_subscription_price(1));
+    fn when_get_a_subscription_return_299_euros() -> Result<(), String> {
+        assert_eq!(299, get_total_subscription_price(1)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_2_subscriptions_return_598_euros() {
-        assert_eq!(598, get_total_subscription_price(2));
+    fn when_get_2_subscriptions_return_598_euros() -> Result<(), String> {
+        assert_eq!(598, get_total_subscription_price(2)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_3_subscriptions_return_717_euros() {
-        assert_eq!(717, get_total_subscription_price(3));
+    fn when_get_3_subscriptions_return_717_euros() -> Result<(), String> {
+        assert_eq!(717, get_total_subscription_price(3)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_10_subscriptions_return_2390_euros() {
-        assert_eq!(2390, get_total_subscription_price(10));
+    fn when_get_10_subscriptions_return_2390_euros() -> Result<(), String> {
+        assert_eq!(2390, get_total_subscription_price(10)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_11_subscriptions_return_2409_euros() {
-        assert_eq!(2409, get_total_subscription_price(11));
+    fn when_get_11_subscriptions_return_2409_euros() -> Result<(), String> {
+        assert_eq!(2409, get_total_subscription_price(11)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_25_subscriptions_return_5475_euros() {
-        assert_eq!(5475, get_total_subscription_price(25));
+    fn when_get_25_subscriptions_return_5475_euros() -> Result<(), String> {
+        assert_eq!(5475, get_total_subscription_price(25)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_26_subscriptions_return_5174_euros() {
-        assert_eq!(5174, get_total_subscription_price(26));
+    fn when_get_26_subscriptions_return_5174_euros() -> Result<(), String> {
+        assert_eq!(5174, get_total_subscription_price(26)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_50_subscriptions_return_9950_euros() {
-        assert_eq!(9950, get_total_subscription_price(50));
+    fn when_get_50_subscriptions_return_9950_euros() -> Result<(), String> {
+        assert_eq!(9950, get_total_subscription_price(50)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_51_subscriptions_return_7599_euros() {
-        assert_eq!(7599, get_total_subscription_price(51));
+    fn when_get_51_subscriptions_return_7599_euros() -> Result<(), String> {
+        assert_eq!(7599, get_total_subscription_price(51)?);
+        Ok(())
     }
 
     #[test]
-    fn when_get_52_subscriptions_return_7748_euros() {
-        assert_eq!(7748, get_total_subscription_price(52));
+    fn when_get_52_subscriptions_return_7748_euros() -> Result<(), String> {
+        assert_eq!(7748, get_total_subscription_price(52)?);
+        Ok(())
+    }
+
+    #[test]
+    fn when_get_0_subscriptions_return_error() {
+        assert!(get_total_subscription_price(0).is_err());
     }
 }