added unit tests

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

@@ -5,13 +5,99 @@ 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) };
+    void qualityNeverNegative() {
+        Item[] items = new Item[] { new Item("fixme", 0, 0) };
         GildedRose app = new GildedRose(items);
         app.updateQuality();
-        assertEquals("fixme", app.items[0].name);
+        assertEquals(0, app.items[0].quality);
     }
 
+    @Test
+    void qualityDegrades2xAfterSellByDate() {
+        Item[] items = new Item[] { new Item("fixme", 1, 10) };
+        GildedRose app = new GildedRose(items);
+
+        // check that quality only goes down 1 while sellIn > 0
+        app.updateQuality();
+        assertEquals(9, app.items[0].quality);
+
+        // check that quality goes down 2 while sellIn <= 0
+        app.updateQuality(); // <- sellIn is now 0
+        assertEquals(7, app.items[0].quality);
+    }
+
+    @Test
+    void qualityIncreasesForAgedBrie() {
+        Item[] items = new Item[] { new Item("Aged Brie", 1, 0) };
+        GildedRose app = new GildedRose(items);
+
+        // NOTE: aged brie increases twice as fast after sellIn days have elapsed
+
+        // quality should go up 1x speed
+        app.updateQuality();
+        assertEquals(1, app.items[0].quality);
+
+        // quality should go up 2x because sellIn is 0
+        app.updateQuality();
+        assertEquals(3, app.items[0].quality);
+    }
+
+    @Test
+    void qualityNeverPasses50() {
+        // aged brie is the only item that increases in quality (besides the pass)
+        Item[] items = new Item[] { new Item("Aged Brie", 1, 49) };
+        GildedRose app = new GildedRose(items);
+
+        // should go up 1 to 50
+        app.updateQuality();
+        assertEquals(50, app.items[0].quality);
+
+        // should stop at 50
+        app.updateQuality();
+        assertEquals(50, app.items[0].quality);
+    }
+
+    @Test
+    void legendaryItemsBehaveAsExpected() {
+        Item[] items = new Item[] { new Item("Sulfuras, Hand of Ragnaros", 0, 80) };
+        GildedRose app = new GildedRose(items);
+
+        app.updateQuality();
+        assertEquals(80, app.items[0].quality);
+    }
+
+    @Test
+    void backstagePassesBehaveAsExpected() {
+        Item[] items = new Item[] { new Item("Backstage passes to a TAFKAL80ETC concert", 10, 5) };
+        GildedRose app = new GildedRose(items);
+
+        // 10 days or less -> grows by 2
+        app.updateQuality(); // sellIn 9
+        assertEquals(7, app.items[0].quality);
+
+        app.updateQuality(); // sellIn 8, quality = 9
+        app.updateQuality(); // sellIn 7, quality = 11
+        app.updateQuality(); // sellIn 6, quality = 13
+
+        // updateQuality
+        //// it will update quality
+        //// it will subtract 1 to sellIn
+        //// TODO: make this clearer when we refactor the actual code
+
+        app.updateQuality(); // sellIn 5, quality = 16 <- is not the case, sellIn 5, quality is 15
+
+        // It changes quality first, and then decreases sellIn
+        assertEquals(15, app.items[0].quality);
+
+        // -1 days -> quality is 0
+        app.updateQuality(); // sellIn 4
+        app.updateQuality(); // sellIn 3
+        app.updateQuality(); // sellIn 2
+        app.updateQuality(); // sellIn 1
+        app.updateQuality(); // sellIn 0
+        app.updateQuality(); // sellIn -1
+
+        assertEquals(0, app.items[0].quality);
+    }
 }