https://github.com/rails/rails/commit/fd6aaaa in Rails 4.2 will remove automatic loading of mocha from the Rails test helper, as it's expected that applications have an explicit dependency on it anyway if they want to use it.

Without it, mocha methods simply don't exist and tests fail with:

NoMethodError: undefined method `any_instance' for #<Class:0x000000070d2670>
    app/models/host.rb:15:in `method_missing'
    test/test_helper.rb:196:in `disable_orchestration'