How do I test a Rails Engine?

I'm writing an engine that interacts with the initialization process of the app. I need to simulate the app boot/start to check if some 开发者_StackOverflow社区initializers were loaded etc.

How do I test this Rails boot/start like a new application booting?

I always create a dummy Rails app in the test folder of my gems and test the gem through the app.

Same for engines, declare it with :path in the gemfile