parametrize default quality rule

Java/src/main/java/com/gildedrose/rules/ConjuredQualityRule.java

@@ -1,16 +1,13 @@
 package com.gildedrose.rules;
 
-import static java.lang.Integer.max;
+public class ConjuredQualityRule extends DefaultQualityRule {
 
-public class ConjuredQualityRule implements QualityRule {
+    public ConjuredQualityRule() {
+        super(2, null, true);
+    }
 
     @Override
     public boolean shouldApply(String itemName) {
         return itemName != null && itemName.startsWith("Conjured ");
     }
-
-    @Override
-    public Result calculateQuality(int oldQuality, int newSellIn) {
-        return new Result(max(oldQuality - 2, 0), true);
-    }
 }

Java/src/main/java/com/gildedrose/rules/DefaultQualityRule.java

@@ -4,20 +4,38 @@ import static java.lang.Integer.max;
 
 public class DefaultQualityRule implements QualityRule {
 
+    private final int multiplier;
+    private final String expectedItemName;
+    private final boolean isFinalRule;
+
+    public DefaultQualityRule() {
+        this(1, null, false);
+    }
+
+    public DefaultQualityRule(int multiplier, String itemName, boolean isFinalRule) {
+        this.multiplier = multiplier;
+        this.expectedItemName = itemName;
+        this.isFinalRule = isFinalRule;
+    }
+
     @Override
     public boolean shouldApply(String itemName) {
-        return true;
+        if (expectedItemName != null) {
+            return expectedItemName.equals(itemName);
+        } else {
+            return true;
+        }
     }
 
     @Override
     public Result calculateQuality(int oldQuality, int newSellIn) {
         final int newQuality;
         if (newSellIn < 0) {
-            newQuality = oldQuality - 2;
+            newQuality = oldQuality - 2 * multiplier;
         } else {
-            newQuality = oldQuality - 1;
+            newQuality = oldQuality - multiplier;
         }
-        return new Result(max(newQuality, 0), false);
+        return new Result(max(newQuality, 0), isFinalRule);
     }
 
 }

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

@@ -29,4 +29,21 @@ class GildedRoseConjuredTest {
         final int expectedQuality = max(initialQuality - 2, 0);
         assertItem(item, ITEM_NAME, 0, expectedQuality);
     }
+
+    @Feature("\"Conjured\" items degrade in Quality twice as fast as normal items")
+    @Feature("The Quality of an item is never negative")
+    @ParameterizedTest(name = "Initial quality: {arguments}")
+    @ValueSource(ints = {0, 1, 2, 3, 49, 50})
+    void shouldDegradeInQualityTwiceFastForOverdueItems(int initialQuality) {
+        // given
+        GildedRose app = prepareApp(new Item(ITEM_NAME, 0, initialQuality));
+
+        // when
+        app.updateQuality();
+
+        // then
+        final Item item = app.items[0];
+        final int expectedQuality = max(initialQuality - 4, 0);
+        assertItem(item, ITEM_NAME, -1, expectedQuality);
+    }
 }