Merge pull request #7257 from KrauseFx/patch-2

Add information about how to run tests

CONTRIBUTING.md

@@ -75,6 +75,10 @@ Code/comments should adhere to the following rules:
 * All changes require test coverage to ensure it does not break during refactor
   work. (There are a few exceptions to this, which can be recognised by there
   not being any coverage for similar code.)
+  * CocoaPods uses [bacon](https://github.com/chneukirchen/bacon) as a test runner.
+    To run all tests, use `bundle exec rake spec` in the root of the 
+    [Rainforest repo](https://github.com/CocoaPods/Rainforest). If you want to run
+    a specific test instead, use `bundle exec bacon spec/[folder]/[name]_spec.rb`
 * All enhancements and bug fixes need to be documented in the CHANGELOG.
 * When writing comments, use properly constructed sentences, including
   punctuation.