README.md in gds-sso-0.4.3 vs README.md in gds-sso-0.5.0

@@ -10,11 +10,11 @@
 For more details on OmniAuth and oAuth2 integration see https://github.com/intridea/omniauth
 
 
 ## Integration with a Rails 3+ app
 
-To use gds-sso tou will need an oauth client ID and secret for sign-on-o-tron or a compatible system.
+To use gds-sso you will need an oauth client ID and secret for sign-on-o-tron or a compatible system.
 These can be provided by one of the team with admin access to sign-on-o-tron.
 
 Then include the gem in your Gemfile:
 
 gem 'gds-sso', :git => 'https://github.com/alphagov/gds-sso.git'
@@ -36,6 +36,17 @@
       config.basic_auth_password = 'secret'
     end
 
 The user model needs to respond to klass.find_by_uid(uid), and must include the GDS::SSO::User module.
 
-You also need to include `GDS::SSO::ControllerMethods` in your ApplicationController
\ No newline at end of file
+You also need to include `GDS::SSO::ControllerMethods` in your ApplicationController
+
+## Use in development mode
+
+In development, you generally want to be able to run an application without needing to run your own SSO server to be running as well. GDS-SSO facilitates this by using a 'mock' mode in development. Mock mode loads an arbitrary user from the local application's user tables:
+
+    GDS::SSO.test_user || GDS::SSO::Config.user_klass.first
+
+To make it use a real strategy (e.g. if you're testing an app against the signon server), set an environment variable when you run your app:
+
+    GDS_SSO_STRATEGY=real bundle exec rails s 
+