Add documentation for system tests

* Document Rails::SystemTestCase
* Document setting drivers with the configration options
* Document using the getter/setter for driver adapters
* Document the CapybaraRackTestDriver and defaults
* Document the CapybaraSeleniumDriver and defaults
* Document custom assertions provided by System Testing
* Document custom form helpers provided by System Testing

1 files changed, 10 insertions, 0 deletions

diff --git a/actionpack/lib/system_testing/driver_adapters.rb b/actionpack/lib/system_testing/driver_adapters.rb
index a8933b4496..d0771f89cb 100644
--- a/actionpack/lib/system_testing/driver_adapters.rb
+++ b/actionpack/lib/system_testing/driver_adapters.rb
@@ -1,4 +1,10 @@
 module SystemTesting
+  # == System Testing Driver Adapters
+  #
+  # System testing supports the following drivers:
+  #
+  # * {RackTest}[https://github.com/brynary/rack-test]
+  # * {Selenium}[https://github.com/SeleniumHQ/selenium]
   module DriverAdapters
     extend ActiveSupport::Autoload
 
@@ -6,6 +12,10 @@ module SystemTesting
     autoload :CapybaraSeleniumDriver
 
     class << self
+      # Returns driver for specified name.
+      #
+      #   SystemTesting::DriverAdapters.lookup(:capybara_selenium_driver)
+      #   # => SystemTesting::DriverAdapters::CapybaraSeleniumDriver
       def lookup(name)
         const_get(name.to_s.camelize)
       end