To re-enable the Create Unit Tests… menu, go to Tools->Customize… to launch the Customize dialog. At the Customize dialog, go to the Commands tab, select the Context menu radio button and choose Editor Context Menus | Code Window.
You will realized that the menu item is actually available in the context menu. 🙂 The VS developers were kind enough to leave it there for us. *HeHe* Click on the Create Unit Tests… menu item and click either Move Up or Move Down. [Note: My screenshot is showing Create Unit Test in singular because I had previously tried to rename it]. Then click Close.
Restart Visual Studio 2012 and whalla! The context menu will be available!