如何在现有的rails引擎中生成虚拟应用程序

I came to work for a company recently that has been working on a specific rails project for a while. Dropped in the middle of the development process, I'm beginning to go back and write tests for the existing code as well as the code currently being produced. Testing the rails 4 app was easy enough, but once I got to testing the engine, I hit a mental block. After doing my due diligence, I found that most people take an approach like this (I came to work for a company recently that has