Implement basic CLI usage help

features/steps/run_steps.rb

@@ -1,4 +1,17 @@
-When /^I start uhwm$/ do
-  @process = run 'uhwm'
-  @interactive = @process
+def uhwm_run options = nil
+  command = %w[uhwm]
+  command << options if options
+  @interactive = @process = run command.join ' '
+end
+
+When /^I start uhwm$/ do
+  uhwm_run
+end
+
+When /^I run uhwm with options? (-.+)$/ do |options|
+  uhwm_run options
+end
+
+Then /^the exit status must be (\d+)$/ do |exit_status|
+  assert_exit_status exit_status.to_i
 end