Create class for normal items

Java/src/main/java/com/gildedrose/items/NormalItem.java

@@ -0,0 +1,20 @@
+package com.gildedrose.items;
+
+import com.gildedrose.Quality;
+import com.gildedrose.SellIn;
+import lombok.EqualsAndHashCode;
+
+@EqualsAndHashCode(callSuper = true)
+public class NormalItem extends GildedRoseItem {
+
+  public NormalItem(String name, SellIn sellIn, Quality quality, boolean conjured) {
+    super(name, sellIn, quality, conjured);
+  }
+
+  @Override
+  protected Quality nextQuality(Quality previous) {
+    Quality nextQuality = previous.copy();
+    nextQuality.decrement();
+    return nextQuality;
+  }
+}

Java/src/test/java/com/gildedrose/items/NormalItemTest.java

@@ -0,0 +1,24 @@
+package com.gildedrose.items;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.gildedrose.Quality;
+import com.gildedrose.SellIn;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+class NormalItemTest {
+
+  @Nested
+  class nextQuality {
+    private final NormalItem item =
+        new NormalItem("+5 Dexterity Vest", SellIn.create(10), Quality.create(1), Boolean.FALSE);
+
+    @Test
+    void should_decrement_quality_in_one() {
+      Quality nextQuality = item.nextQuality(Quality.create(1));
+
+      assertThat(nextQuality.getValue()).isZero();
+    }
+  }
+}