setCommand(new HelloCommand($receiver)); $invoker->run(); $this->assertSame('Hello World', $receiver->getOutput()); $messageDateCommand = new AddMessageDateCommand($receiver); $messageDateCommand->execute(); $invoker->run(); $this->assertSame("Hello World\nHello World [".date('Y-m-d').']', $receiver->getOutput()); $messageDateCommand->undo(); $invoker->run(); $this->assertSame("Hello World\nHello World [".date('Y-m-d')."]\nHello World", $receiver->getOutput()); } }