Refactor and group regular item logic.

Author: aaccioly

Java/src/main/java/com/gildedrose/GildedRose.java

@@ -36,15 +36,16 @@ public void updateQuality() {
     private void updateItem(Item item) {
         if (isLegendary(item.name)) {
             return;
-        } else if (isAgedBrie(item.name)) {
-            item.sellIn--;
+        }
+
+        item.sellIn--;
+
+        if (isAgedBrie(item.name)) {
             if (item.quality < 50) {
                 var qualityDelta = item.sellIn < 0 ? 2 : 1;
                 item.quality += qualityDelta;
             }
-            return;
         } else if (isBackStagePass(item.name)) {
-            item.sellIn--;
             if (item.sellIn < 0) {
                 item.quality = 0;
             } else {
@@ -53,15 +54,9 @@ private void updateItem(Item item) {
                     item.quality += qualityDelta;
                 }
             }
-            return;
-        }
-
-        // all items except Sulfuras -> decrease sellIn
-        item.sellIn = item.sellIn - 1;
-
-        if (item.quality > 0) {
+        } else { // regular item
             var qualityDelta = item.sellIn < 0 ? 2 : 1;
-            item.quality = item.quality - qualityDelta;
+            item.quality = Math.max(0, item.quality - qualityDelta);
         }
     }
 }

Java/src/test/java/com/gildedrose/GildedRoseTest.java

@@ -129,6 +129,45 @@ void qualityIncreasesBy3WhenSellInIsBetween5And0() {
         }
     }
 
+    @Nested
+    class NormalItem {
+        private final Item normalItem = new Item("Foo", 10, 20);
+
+        @DisplayName("quality decreases by 1")
+        @Test
+        void qualityDecreasesBy1() {
+            GildedRose app = createGildedRose(normalItem);
+            app.updateQuality();
+            assertThat(normalItem.quality).isEqualTo(19);
+        }
+
+        @DisplayName("sellIn decreases by 1")
+        @Test
+        void sellInDecreasesBy1() {
+            GildedRose app = createGildedRose(normalItem);
+            app.updateQuality();
+            assertThat(normalItem.sellIn).isEqualTo(9);
+        }
+
+        @DisplayName("quality decreases by 2 after sellIn date")
+        @Test
+        void qualityDecreasesBy2AfterSellIn() {
+            normalItem.sellIn = 0;
+            GildedRose app = createGildedRose(normalItem);
+            app.updateQuality();
+            assertThat(normalItem.quality).isEqualTo(18);
+        }
+
+        @DisplayName("quality never goes below 0")
+        @Test
+        void qualityNeverGoesBelow0() {
+            normalItem.quality = 0;
+            GildedRose app = createGildedRose(normalItem);
+            app.updateQuality();
+            assertThat(normalItem.quality).isEqualTo(0);
+        }
+    }
+
     public GildedRose createGildedRose(Item item) {
         return new GildedRose(item);
     }