class Spec::Rails::Example::ControllerExampleGroup

def integrate_views(integrate_views = true)

information about Integration and Isolation modes.
See Spec::Rails::Example::ControllerExampleGroup for more

...
integrate_views
describe ThingController do

your controller examples in Integration mode.
Use integrate_views to instruct RSpec to render views in 
def integrate_views(integrate_views = true)
  @integrate_views = integrate_views
end