Add unit tests for AgedBrieItem increasing quality

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

@@ -0,0 +1,24 @@
+package com.gildedrose;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class AgedBrieItemTest {
+
+    @Test
+    void agedBrieIncreasesQuality() {
+        Item item = new Item("Aged Brie", 2, 0);
+        GildedRose app = new GildedRose(new Item[]{item});
+        app.updateQuality();
+        assertEquals(1, item.quality);
+        assertEquals(1, item.sellIn);
+    }
+
+    @Test
+    void qualityNeverExceeds50() {
+        Item item = new Item("Aged Brie", 2, 50);
+        GildedRose app = new GildedRose(new Item[]{item});
+        app.updateQuality();
+        assertEquals(50, item.quality);
+    }
+}