Add unit tests for GildedRose item updateQuality method

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

@@ -1,17 +1,106 @@
 package com.gildedrose;
 
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
+@DisplayName("Gilded Rose 테스트")
 class GildedRoseTest {
+    private Item[] items;
+    private GildedRose app;
 
-    @Test
-    void foo() {
-        Item[] items = new Item[]{new Item("fixme", 0, 0)};
-        GildedRose app = new GildedRose(items);
-        app.updateQuality();
-        assertEquals("fixme", app.items[0].name);
+    private void setup(String name, int sellIn, int quality) {
+        items = new Item[]{new Item(name, sellIn, quality)};
+        app = new GildedRose(items);
     }
 
+    private int itemSellIn() {
+        return app.items[0].sellIn;
+    }
+
+    private int itemQuality() {
+        return app.items[0].quality;
+    }
+
+    @Nested
+    @DisplayName("일반 아이템은")
+    class StandardItem {
+
+        @Test
+        @DisplayName("하루가 지나면 Quality와 sellIn이 1씩 감소한다")
+        void qualityAndSellInDecrease() {
+            GildedRoseTest.this.setup("Standard Item", 10, 20);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(19);
+            assertThat(itemSellIn()).isEqualTo(9);
+        }
+    }
+
+    @Nested
+    @DisplayName("'Aged Brie'는")
+    class AgedBrie {
+        @Test
+        @DisplayName("하루가 지나면 Quality는 증가하지만 sellIn은 감소한다")
+        void qualityIncreasesSellInDecreases() {
+            GildedRoseTest.this.setup("Aged Brie", 10, 20);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(21);
+            assertThat(itemSellIn()).isEqualTo(9);
+        }
+    }
+
+    @Nested
+    @DisplayName("'Backstage passes'는")
+    class BackstagePasses {
+        @Test
+        @DisplayName("10일 초과 남았을 때 하루가 지나면 품질이 1 씩 증가하고 sellIn은 감소한다")
+        void quality1IncreasesSellInDecreasesMoreThan10Days() {
+            GildedRoseTest.this.setup("Backstage passes to a TAFKAL80ETC concert", 15, 20);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(21);
+            assertThat(itemSellIn()).isEqualTo(14);
+        }
+
+        @Test
+        @DisplayName("6일에서 10일 남았을 때 하루가 지나면 품질이 2 씩 증가하고 sellIn은 감소한다")
+        void quality2IncreasesSellInDecreases6to10Days() {
+            GildedRoseTest.this.setup("Backstage passes to a TAFKAL80ETC concert", 10, 20);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(22);
+            assertThat(itemSellIn()).isEqualTo(9);
+        }
+
+        @Test
+        @DisplayName("5일 미만 남았을 때 하루가 지나면 품질이 3 씩 증가하고 sellIn은 감소한다")
+        void quality3IncreasesSellInDecreasesLessThan6Days() {
+            GildedRoseTest.this.setup("Backstage passes to a TAFKAL80ETC concert", 5, 20);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(23);
+            assertThat(itemSellIn()).isEqualTo(4);
+        }
+
+        @Test
+        @DisplayName("콘서트가 끝나면(즉, sellIn이 0 이하가 되면) 품질은 0이된다.")
+        void qualityDropsToZeroAfterTheConcert() {
+            GildedRoseTest.this.setup("Backstage passes to a TAFKAL80ETC concert", 0, 20);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(0);
+        }
+    }
+
+    @Nested
+    @DisplayName("'Sulfuras'는")
+    class Sulfuras {
+
+        @Test
+        @DisplayName("하루가 지나도 품질과 sellIn은 변하지 않는다")
+        void qualityAndSellInUnchanged() {
+            GildedRoseTest.this.setup("Sulfuras, Hand of Ragnaros", 10, 80);
+            app.updateQuality();
+            assertThat(itemQuality()).isEqualTo(80);
+            assertThat(itemSellIn()).isEqualTo(10);
+        }
+    }
 }