88 - Added undo example for command pattern

Behavioral/Command/Tests/UndoableCommandTest.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace DesignPatterns\Behavioral\Command\Tests;
+
+use DesignPatterns\Behavioral\Command\AddMessageDateCommand;
+use DesignPatterns\Behavioral\Command\HelloCommand;
+use DesignPatterns\Behavioral\Command\Invoker;
+use DesignPatterns\Behavioral\Command\Receiver;
+use PHPUnit_Framework_TestCase;
+
+/**
+ * UndoableCommandTest has the role of the Client in the Command Pattern.
+ */
+class UndoableCommandTest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * @var Invoker
+     */
+    protected $invoker;
+
+    /**
+     * @var Receiver
+     */
+    protected $receiver;
+
+    protected function setUp()
+    {
+        $this->invoker = new Invoker();
+        $this->receiver = new Receiver();
+    }
+
+    public function testInvocation()
+    {
+        $this->invoker->setCommand(new HelloCommand($this->receiver));
+        $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), 'Hello World');
+
+        $messageDateCommand = new AddMessageDateCommand($this->receiver);
+        $messageDateCommand->execute();
+
+        $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), "Hello World\nHello World [".date('Y-m-d').']');
+
+        $messageDateCommand->undo();
+
+        $this->invoker->run();
+        $this->assertEquals($this->receiver->getOutput(), "Hello World\nHello World [".date('Y-m-d')."]\nHello World");
+    }
+}