Add integration tests for current requirements

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

@@ -7,11 +7,123 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 class GildedRoseTest {
 
     @Test
-    void foo() {
-        Item[] items = new Item[] { new Item("foo", 0, 0) };
-        GildedRose app = new GildedRose(items);
-        app.updateQuality();
-        assertEquals("fixme", app.items[0].name);
+    void givenItem_whenExpiryDateApproaches_thenSellInAndQualityDecreases() {
+        int defaultItemSellIn = 10;
+        int defaultItemQuality = 20;
+        int agedBrieSellIn = 2;
+        int agedBrieQuality = 0;
+        int backstagePassSellIn = 15;
+        int backstagePassQuality = 20;
+        GildedRose app = updateQuality(
+            createDefaultItem(defaultItemSellIn, defaultItemQuality),
+            createAgedBrieItem(agedBrieSellIn, agedBrieQuality),
+            createBackstagePass(backstagePassSellIn, backstagePassQuality)
+        );
+
+        assertEquals(defaultItemSellIn - 1, app.items[0].sellIn);
+        assertEquals(defaultItemQuality - 1, app.items[0].quality);
+        assertEquals(agedBrieSellIn - 1, app.items[1].sellIn);
+        assertEquals(backstagePassSellIn - 1, app.items[2].sellIn);
     }
 
+    @Test
+    void givenItemWithExpiredDate_whenUpdateQuality_thenQualityDecreasesTwiceAsFast() {
+        int quality = 5;
+        GildedRose app = updateQuality(createDefaultItem(0, 5));
+
+        assertEquals(quality - 2, app.items[0].quality);
+    }
+
+    @Test
+    void givenItemWithExpiredDate_whenUpdateQuality_thenQualityIsNeverNegative() {
+        GildedRose app = updateQuality(createDefaultItem(0, 1));
+
+        assertEquals(0, app.items[0].quality);
+
+        app.updateQuality();
+
+        assertEquals(0, app.items[0].quality);
+    }
+
+    @Test
+    void givenAgedBrieWithWithHighQuality_whenUpdateQuality_thenQualityIsNeverAboveMaximum() {
+        GildedRose app = updateQuality(createAgedBrieItem(10, 49));
+
+        assertEquals(50, app.items[0].quality);
+
+        app.updateQuality();
+
+        assertEquals(50, app.items[0].quality);
+    }
+
+    @Test
+    void givenAgedBrieOrBackstagePass_whenUpdateQuality_thenQualityIncreases() {
+        int agedBrieQuality = 12;
+        int backstagePassQuality = 8;
+        GildedRose app = updateQuality(
+            createAgedBrieItem(10, agedBrieQuality),
+            createBackstagePass(17, backstagePassQuality)
+        );
+
+        assertEquals(agedBrieQuality + 1, app.items[0].quality);
+        assertEquals(backstagePassQuality + 1, app.items[1].quality);
+    }
+
+    @Test
+    void givenBackstagePassLessThan10sellInDays_whenUpdateQuality_thenQualityIncreasesDouble() {
+        int quality = 8;
+        GildedRose app = updateQuality(createBackstagePass(9, quality));
+
+        assertEquals(quality + 2, app.items[0].quality);
+    }
+
+    @Test
+    void givenBackstagePassLessThan5sellInDays_whenUpdateQuality_thenQualityIncreasesWithFactor3() {
+        int quality = 7;
+        GildedRose app = updateQuality(createBackstagePass(3, quality));
+
+        assertEquals(quality + 3, app.items[0].quality);
+    }
+
+    @Test
+    void givenBackstagePassBeyondSellInDays_whenUpdateQuality_thenQualityIsZero() {
+        int quality = 13;
+        GildedRose app = updateQuality(createBackstagePass(0, quality));
+
+        assertEquals(0, app.items[0].quality);
+
+        app.updateQuality();
+
+        assertEquals(0, app.items[0].quality);
+    }
+
+    @Test
+    void givenLegendaryItem_whenUpdateQuality_thenQualityDoesNotChange() {
+        int quality = 34;
+        GildedRose app = updateQuality(createLegendaryItem(quality));
+
+        assertEquals(quality, app.items[0].quality);
+    }
+
+    private GildedRose updateQuality(Item... items) {
+        GildedRose app = new GildedRose(items);
+        app.updateQuality();
+        return app;
+    }
+
+    private Item createDefaultItem(int sellIn, int quality) {
+        return new Item("+5 Dexterity Vest", sellIn, quality);
+    }
+
+    private Item createAgedBrieItem(int sellIn, int quality) {
+        return new Item("Aged Brie", sellIn, quality);
+    }
+
+    private Item createBackstagePass(int sellIn, int quality) {
+        return new Item("Backstage passes to a TAFKAL80ETC concert", sellIn, quality);
+    }
+
+    private Item createLegendaryItem(int quality) {
+        return new Item("Sulfuras, Hand of Ragnaros", 10, quality);
+    }
 }