rails/rails — pull request #7477 by kennyj (2012-08-29 14:27:18+00:00)
Title: Added missing require. When performing rake test:isolated, test/base_test.rb was break.

I fixed some warnings related to `mime_type` method's deprecation (#7469).

But I got another problem.
When performing rake test:isolated in ActionMailer, test/base_test.rb was break.

```
1) Failure:
test_0007_should set template content type if mail has only one part(BaseTest) [test/base_test.rb:69]:
Expected: "text/html"
Actual: "text/plain"
...
```

After investigating, I realized the cause of problem.
We didn't load `action_dispatch`, thus we didn't call `ActionView::Template::Types.delegate_to Mime`