Adds scenario for the ambiguous step reporting

features/docs/defining_steps/ambiguous_steps.feature

@@ -0,0 +1,89 @@
+Feature: Ambiguous Steps
+
+  When Cucumber searches for a step definition for a step, it might find multiple step
+  definitions that could match. In that case, it will give you an error that the step
+  definitions are ambiguous.
+
+  You can also use a `--guess` mode, where it uses magic powers to try and figure
+  out which of those two step definitions is most likely to be the one you meant it
+  to use. Use it with caution!
+
+
+  Scenario: Ambiguous steps
+
+    Given a file named "features/ambiguous.feature" with:
+    """
+    Feature:
+
+      Scenario:
+      When a step
+      Then an ambiguous step
+
+    """
+    And a file named "features/step_definitions.rb" with:
+    """
+      When(/^a.*step$/) do
+        'foo'
+      end
+
+      Then(/^an ambiguous step$/) do
+        'bar'
+      end
+
+    """
+    When I run `cucumber`
+    Then it should fail with:
+    """
+          Ambiguous match of "an ambiguous step":
+
+          features/step_definitions.rb:1:in `/^a.*step$/'
+          features/step_definitions.rb:5:in `/^an ambiguous step$/'
+
+          You can run again with --guess to make Cucumber be more smart about it
+           (Cucumber::Ambiguous)
+          features/ambiguous.feature:5:in `Then an ambiguous step'
+
+    Failing Scenarios:
+    cucumber features/ambiguous.feature:3 # Scenario: 
+
+    1 scenario (1 failed)
+    2 steps (1 failed, 1 passed)
+    0m0.012s
+
+    """
+
+
+  Scenario: Ambiguous steps with guess mode
+
+    Given a file named "features/ambiguous.feature" with:
+    """
+    Feature:
+
+      Scenario:
+      When a step
+      Then an ambiguous step
+    """
+    And a file named "features/step_definitions.rb" with:
+    """
+      When(/^a.*step$/) do
+        'foo'
+      end
+
+      Then(/^an ambiguous step$/) do
+        'bar'
+      end
+    """
+    When I run `cucumber -g`
+    Then it should pass with exactly:
+    """
+    Feature: 
+
+      Scenario:                # features/ambiguous.feature:3
+        When a step            # features/step_definitions.rb:1
+        Then an ambiguous step # features/step_definitions.rb:5
+
+    1 scenario (1 passed)
+    2 steps (2 passed)
+    0m0.012s
+
+    """

lib/cucumber/filters/activate_steps.rb

@@ -43,7 +43,12 @@ def initialize(step_match_search, configuration, test_step)
           end
 
           def result
-            return NoStepMatch.new(test_step.source.last, test_step.name) unless matches.any?
+            begin
+              return NoStepMatch.new(test_step.source.last, test_step.name) unless matches.any?
+            rescue Cucumber::Ambiguous => e
+              return AmbiguousStepMatch.new(e)
+            end
+
             configuration.notify :step_activated, test_step, match
             return SkippingStepMatch.new if configuration.dry_run?
             match

lib/cucumber/step_match.rb

@@ -139,4 +139,17 @@ def activate(test_step)
       return test_step
     end
   end
+
+  class AmbiguousStepMatch
+
+    def initialize(error)
+      @error = error
+    end
+
+    def activate(test_step)
+      return test_step.with_action { raise @error }
+    end
+
+  end
+
 end