added unit test for delegate

groovier-plugin/src/test/groovy/com/ericlam/mc/groovytest/TestGroovyDelegate.groovy

@@ -0,0 +1,80 @@
+package com.ericlam.mc.groovytest
+
+import org.bukkit.Material
+import org.junit.jupiter.api.Test
+
+class TestGroovyDelegate {
+
+    @Test
+    void testGroovyDelegate() {
+        def builder = new ItemBuilderImpl() as ItemBuilder
+        builder.item = new Item()
+        builder.meta = builder.item.meta
+
+        builder.with {
+            type = Material.DIAMOND
+            displayName = "Hello Diamond!"
+            lore = ["Hello", "Diamond!"]
+        }
+
+        println builder.item.toString()
+    }
+
+
+    trait ItemBuilder {
+        @Delegate Item item
+        @Delegate ItemMeta meta
+    }
+
+    class ItemBuilderImpl implements ItemBuilder {
+        ItemBuilderImpl(){
+            this.item = new Item()
+            this.meta = item.meta
+        }
+    }
+
+
+    class Item {
+        private Material type = Material.STONE
+        private ItemMeta meta = new ItemMeta()
+
+        void setType(Material type) {
+            this.type = type
+        }
+
+        ItemMeta getMeta() {
+            return meta
+        }
+
+
+        @Override
+        public String toString() {
+            return "Item{" +
+                    "type=" + type +
+                    ", meta=" + meta +
+                    '}';
+        }
+    }
+
+    class ItemMeta {
+        private String displayName;
+        private List<String> lore;
+
+        void setDisplayName(String displayName) {
+            this.displayName = displayName
+        }
+
+        void setLore(List<String> lore) {
+            this.lore = lore
+        }
+
+
+        @Override
+        public String toString() {
+            return "ItemMeta{" +
+                    "displayName='" + displayName + '\'' +
+                    ", lore=" + lore +
+                    '}';
+        }
+    }
+}