Register a Layout with display information

features/layout/registration.feature

@@ -0,0 +1,13 @@
+Feature: layout registration
+
+  Scenario: sends the #register message to the layout with the display
+    Given a file named layout.rb with:
+      """
+      class Layout
+        def register display
+          puts display
+        end
+      end
+      """
+    When I run uhwm with option -r./layout -l Layout
+    Then the current output must contain current display

features/steps/filesystem_steps.rb

@@ -0,0 +1,3 @@
+Given /^a file named ([^ ]+) with:$/ do |path, content|
+  write_file path, content
+end

features/steps/output_steps.rb

@@ -31,3 +31,11 @@ end
 Then /^the current output must match \/([^\/]+)\/([a-z]*)$/ do |pattern, options|
   uhwm_wait_output Regexp.new(pattern, options)
 end
+
+Then /^the current output must contain:$/ do |content|
+  uhwm_wait_output content.to_s
+end
+
+Then /^the current output must contain current display$/ do
+  uhwm_wait_output ENV['DISPLAY']
+end