introduce tests for all item types

these provide something to test future refactor against. conjured test is disabled as the functionality isn't provided initially in the code we're supposed to refactor.

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

@@ -1,17 +1,130 @@
 package com.gildedrose;
 
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 class GildedRoseTest {
-
     @Test
-    void foo() {
-        Item[] items = new Item[] { new Item("foo", 0, 0) };
+    @DisplayName("Regular item")
+    void updateQualityRegularItem() {
+        Item itemUnderTest = new Item("Sample Regular Item", 1, 5);
+        Item[] items = new Item[] { itemUnderTest };
         GildedRose app = new GildedRose(items);
+
         app.updateQuality();
-        assertEquals("fixme", app.items[0].name);
+        assertEquals(0, itemUnderTest.sellIn);
+        assertEquals(4, itemUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-1, itemUnderTest.sellIn);
+        assertEquals(2, itemUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-2, itemUnderTest.sellIn);
+        assertEquals(0, itemUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-3, itemUnderTest.sellIn);
+        assertEquals(0, itemUnderTest.quality);
     }
 
+    @Test
+    @DisplayName("Aged Brie")
+    void updateQualityAgedBrie() {
+        Item agedBrieUnderTest = new Item("Aged Brie", 1, 46);
+        Item[] items = new Item[] { agedBrieUnderTest };
+        GildedRose app = new GildedRose(items);
+
+        app.updateQuality();
+        assertEquals(0, agedBrieUnderTest.sellIn);
+        assertEquals(47, agedBrieUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-1, agedBrieUnderTest.sellIn);
+        assertEquals(49, agedBrieUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-2, agedBrieUnderTest.sellIn);
+        assertEquals(50, agedBrieUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-3, agedBrieUnderTest.sellIn);
+        assertEquals(50, agedBrieUnderTest.quality);
+    }
+
+    @Test
+    @DisplayName("Sulfuras")
+    void updateQualitySulfuras() {
+        Item sulfurasUnderTest = new Item("Sulfuras, Hand of Ragnaros", 23, 80);
+        Item[] items = new Item[] { sulfurasUnderTest };
+        GildedRose app = new GildedRose(items);
+
+        app.updateQuality();
+        assertEquals(23, sulfurasUnderTest.sellIn);
+        assertEquals(80, sulfurasUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(23, sulfurasUnderTest.sellIn);
+        assertEquals(80, sulfurasUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(23, sulfurasUnderTest.sellIn);
+        assertEquals(80, sulfurasUnderTest.quality);
+    }
+
+    @Test
+    @DisplayName("Backstage Pass")
+    void updateQualityBackstagePasses() {
+        Item bPass11days2event = new Item("Backstage passes to a TAFKAL80ETC concert", 11, 25);
+        Item bPass10days2event = new Item("Backstage passes to a TAFKAL80ETC concert", 10, 25);
+        Item bPass5days2event = new Item("Backstage passes to a TAFKAL80ETC concert", 5, 25);
+        Item bPass1dayB4event = new Item("Backstage passes to a TAFKAL80ETC concert", 1, 47);
+        Item[] items = new Item[] {
+            bPass11days2event, bPass10days2event,
+            bPass5days2event, bPass1dayB4event
+        };
+        GildedRose app = new GildedRose(items);
+
+        app.updateQuality();
+        assertEquals(26, bPass11days2event.quality); //now 10 days
+        assertEquals(27, bPass10days2event.quality); //now 9 days
+        assertEquals(28, bPass5days2event.quality); //now 4 days
+        assertEquals(50, bPass1dayB4event.quality); //now event day
+
+        app.updateQuality();
+        assertEquals(28, bPass11days2event.quality); //now 9 days
+        assertEquals(29, bPass10days2event.quality); //now 8 days
+        assertEquals(31, bPass5days2event.quality); //now 3 days
+        assertEquals(0, bPass1dayB4event.quality); //past event date
+
+        app.updateQuality();
+        assertEquals(30, bPass11days2event.quality); //now 8 days
+        assertEquals(31, bPass10days2event.quality); //now 7 days
+        assertEquals(34, bPass5days2event.quality); //now 2 days
+        assertEquals(0, bPass1dayB4event.quality); //past event date
+    }
+
+    @Test
+    @Disabled
+    @DisplayName("Conjured Item")
+    void updateQualityConjuredItem() {
+        Item conjuredItemUnderTest = new Item("Conjured Sample Item", 1, 8);
+        Item[] items = new Item[] { conjuredItemUnderTest };
+        GildedRose app = new GildedRose(items);
+
+        app.updateQuality();
+        assertEquals(0, conjuredItemUnderTest.sellIn);
+        assertEquals(6, conjuredItemUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-1, conjuredItemUnderTest.sellIn);
+        assertEquals(2, conjuredItemUnderTest.quality);
+
+        app.updateQuality();
+        assertEquals(-2, conjuredItemUnderTest.sellIn);
+        assertEquals(0, conjuredItemUnderTest.quality);
+    }
 }