Fix informed seed when not explicitly passed

If you don't explicitly pass a seed, cucumber would inform it has run
test with an incorrect seed, so it would be impossible to actually
reproduce a failing run.

features/docs/cli/randomize.feature

@@ -101,6 +101,11 @@ Feature: Randomize
 
       """
 
+  Scenario: Rerun scenarios randomized
+    When I run `cucumber --order random --format summary`
+    And I rerun the previous command with the same seed
+    Then the output of both commands should be the same
+
   @spawn @todo-windows
   Scenario: Run scenarios randomized with some skipped
     When I run `cucumber --tags 'not @skipme' --order random:41544 -q`

features/lib/step_definitions/cucumber_steps.rb

@@ -66,6 +66,20 @@
   run_feature features.first, formatter
 end
 
+When(/^I rerun the previous command with the same seed$/) do
+  previous_seed = last_command_started.output.match(/with seed (\d+)/)[1]
+  second_command = all_commands.last.commandline.gsub(/random/, "random:#{previous_seed}")
+
+  step "I run `#{second_command}`"
+end
+
+Then(/the output of both commands should be the same/) do
+  first_output = all_commands.first.output.gsub(/\d+m\d+\.\d+s/, '')
+  last_output = all_commands.last.output.gsub(/\d+m\d+\.\d+s/, '')
+
+  expect(first_output).to eq(last_output)
+end
+
 module CucumberHelper
   def run_feature(filename = 'features/a_feature.feature', formatter = 'progress')
     run_simple "#{Cucumber::BINARY} #{filename} --format #{formatter}", false

lib/cucumber/cli/configuration.rb

@@ -108,7 +108,7 @@ def paths
       end
 
       def to_hash
-        Hash(@options).merge(out_stream: @out_stream, error_stream: @error_stream)
+        Hash(@options).merge(out_stream: @out_stream, error_stream: @error_stream, seed: seed)
       end
 
       private