commits tests for testing decorator pattern.

src/test/java/com/designpatterns/decorator/DecoratorDemo.java

+package com.designpatterns.decorator;
+
+import com.designpatterns.structural.decorator.EmailSender;
+import com.designpatterns.structural.decorator.EncodingDecorator;
+import com.designpatterns.structural.decorator.Sender;
+import com.designpatterns.structural.decorator.SenderDecorator;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.Base64;
+
+public class DecoratorDemo {
+
+    @Test
+    public void testDecorator_sendEmailAsPlainText() {
+        String message = "test message";
+        EmailSender sender = new EmailSender();
+        String content = sender.send(message);
+
+        Assertions.assertEquals(content, message);
+
+    }
+
+    @Test
+    public void testDecorator_sendEmailAsEncodedTest() {
+        String message = "test message";
+        Sender sender = new SenderDecorator(
+                new EncodingDecorator(
+                        new EmailSender()
+                )
+        );
+
+        String encodedContent = sender.send(message);
+
+        Assertions.assertEquals(
+                new String(Base64.getDecoder().decode (encodedContent)),
+                message
+        );
+
+
+
+    }
+}