Add immutable quality behavior

Quality does not change. Ever

Java/src/main/java/com/gildedrose/behavior/quality/ImmutableQualityBehavior.java

@@ -0,0 +1,16 @@
+package com.gildedrose.behavior.quality;
+
+import com.gildedrose.Item;
+
+public class ImmutableQualityBehavior implements QualityBehavior {
+
+    public static ImmutableQualityBehavior newInstance() {
+        return new ImmutableQualityBehavior();
+    }
+
+    @Override
+    public void processQualityUpdate(Item item) {
+
+    }
+
+}

Java/src/test/java/com/gildedrose/behavior/quality/ImmutableQualityBehaviorTest.java

@@ -0,0 +1,45 @@
+package com.gildedrose.behavior.quality;
+
+import com.gildedrose.Item;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ImmutableQualityBehaviorTest {
+
+    private QualityBehavior qualityBehavior;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        qualityBehavior = new ImmutableQualityBehavior();
+    }
+
+    @Test
+    void immutableQuality() {
+        Item item = getItem(10);
+        qualityBehavior.processQualityUpdate(item);
+
+        assertEquals(10, item.quality);
+    }
+
+    @Test
+    void immutableQualityZero() {
+        Item item = getItem(0);
+        qualityBehavior.processQualityUpdate(item);
+
+        assertEquals(0, item.quality);
+    }
+
+    @Test
+    void immutableQualityNegative() {
+        Item item = getItem(-10);
+        qualityBehavior.processQualityUpdate(item);
+
+        assertEquals(-10, item.quality);
+    }
+
+    private Item getItem(int quality) {
+        return new Item("SomeItem", 0, quality);
+    }
+}