diff --git a/README.md b/README.md
index b42865eee..2df9f7f8c 100644
--- a/README.md
+++ b/README.md
@@ -61,3 +61,15 @@ This is still a work in progress; some step definition mappings are missing to r
 You can run the following script which will execute cucumber.js recursively against all known passing features and "core.feature":
 
     $ ./run_all_features.js
+
+### Debug messages
+
+You can display debug messages by setting the DEBUG_LEVEL environment variable. It goes from `1` to `5`. `5` will diplay everything, `1` will only print out the critical things.
+
+    $ DEBUG_LEVEL=5 ./run_all_features.js
+    $ DEBUG_LEVEL=5 ./cucumber.js features/cucumber-features/core.feature
+
+It even works with Aruba:
+
+    $ rm -rf doc; DEBUG_LEVEL=5 ARUBA_REPORT_DIR=doc cucumber features/cucumber-features/core.feature -r features
+    $ open doc/features/cucumber-features/*.html # you'll see debug messages in Aruba-generated docs
diff --git a/features/step_definitions/cucumber_js_mappings.rb b/features/step_definitions/cucumber_js_mappings.rb
index 9b1a9aa76..126d65ef7 100644
--- a/features/step_definitions/cucumber_js_mappings.rb
+++ b/features/step_definitions/cucumber_js_mappings.rb
@@ -1,4 +1,3 @@
-# FIXME: Rename to CucumberJsMappings?
 module CucumberJsMappings
   STEP_DEFINITIONS_FILE = "features/step_definitions/cucumber_steps.js"
   FEATURE_FILE          = "features/a_feature.feature"
diff --git a/features/step_definitions/cucumber_steps.js b/features/step_definitions/cucumber_steps.js
index 8f9cf0be2..7616d0e33 100644
--- a/features/step_definitions/cucumber_steps.js
+++ b/features/step_definitions/cucumber_steps.js
@@ -1,4 +1,178 @@
 var cucumberSteps = function() {
+  var shouldPrepare = true;
+  var featureSource;
+  var stepDefinitions;
+  var touchedSteps;
+  var lastRunSucceeded;
+  var lastRunOutput;
 
+  Given(/^a scenario "([^"]*)" with:$/, function(scenarioName, steps, callback) {
+    prepare();
+    featureSource += "Feature: A feature\n";
+    featureSource += "  Scenario: " + scenarioName + "\n";
+    featureSource += steps.replace(/^/gm, '    ');
+    callback();
+  });
+
+  Given(/^the step "([^"]*)" has a passing mapping$/, function(stepName, callback) {
+    prepare();
+    stepDefinitions += "Given(/^" + stepName + "$/, function(callback) {\
+  touchStep(\"" + stepName + "\");\
+  callback();\
+});\n";
+    callback();
+  });
+
+  Given(/^the step "([^"]*)" has a failing mapping$/, function(stepName, callback) {
+    prepare();
+    stepDefinitions += "Given(/^" + stepName + "$/, function(callback) {\
+  touchStep(\"" + stepName + "\");\
+  throw('I was supposed to fail.');\
+});\n";
+    callback();
+  });
+
+  Given(/^the step "([^"]*)" has a pending mapping$/, function(stepName, callback) {
+    prepare();
+    stepDefinitions += "Given(/^" + stepName + "$/, function(callback) {\
+  touchStep(\"" + stepName + "\");\
+  callback.pending('I am pending.');\
+});\n";
+    callback();
+  });
+
+  Given(/^the following feature:$/, function(feature, callback) {
+    prepare();
+    featureSource = feature;
+    callback();
+  });
+
+  When(/^Cucumber executes the scenario "([^"]*)"$/, function(scenarioName, callback) {
+    runFeature(callback);
+  });
+
+  When(/^Cucumber runs the feature$/, function(callback) {
+    runFeature(callback);
+  });
+
+  When(/^Cucumber runs the scenario with steps for a calculator$/, function(callback) {
+    RpnCalculator = require('../support/rpn_calculator');
+    supportCode = function() { require('./calculator_steps')(RpnCalculator) };
+    runFeatureWithSupportCodeSource(supportCode, callback);
+  });
+
+  Then(/^the scenario passes$/, function(callback) {
+    if (!lastRunSucceeded)
+      throw("Expected the scenario to pass but it failed");
+    callback();
+  });
+
+  Then(/^the scenario fails$/, function(callback) {
+    assertFailedScenario();
+    callback();
+  });
+
+  Then(/^the scenario is pending$/, function(callback) {
+    assertPendingScenario();
+    callback();
+  });
+
+  Then(/^the scenario is undefined$/, function(callback) {
+    assertUndefinedScenario();
+    callback();
+  });
+
+  Then(/^the step "([^"]*)" is skipped$/, function(stepName, callback) {
+    assertSkippedStep(stepName);
+    callback();
+  });
+
+  Then(/^the feature passes$/, function(callback) {
+    assertPassingFeature();
+    callback();
+  });
+
+  function prepare() {
+    if (shouldPrepare) {
+      shouldPrepare = false;
+      touchedSteps    = [];
+      featureSource   = "";
+      stepDefinitions = "";
+    }
+  }
+
+  function runFeature(callback) {
+    var supportCode;
+    var supportCodeSource = "supportCode = function() {\n" + stepDefinitions + "};\n";
+    eval(supportCodeSource);
+    runFeatureWithSupportCodeSource(supportCode, callback);
+  }
+
+  function runFeatureWithSupportCodeSource(supportCode, callback) {
+    var Cucumber          = require('../../lib/cucumber');
+    var cucumber          = Cucumber(featureSource, supportCode);
+    var formatter         = Cucumber.Listener.ProgressFormatter({logToConsole: false});
+    cucumber.attachListener(formatter);
+    cucumber.start(function(succeeded) {
+      lastRunSucceeded = succeeded;
+      lastRunOutput    = formatter.getLogs();
+      Cucumber.Debug.notice(lastRunOutput, 'cucumber output', 5);
+      shouldPrepare = true;
+      callback();
+    });
+  }
+
+  function touchStep(string) {
+    touchedSteps.push(string);
+  }
+
+  function isStepTouched(pattern) {
+    return (touchedSteps.indexOf(pattern) >= 0);
+  }
+
+  function assertPassingFeature() {
+    assertNoPartialOutput("failed", lastRunOutput);
+    assertSuccess();
+  }
+
+  function assertFailedScenario() {
+    assertPartialOutput("1 scenario (1 failed)", lastRunOutput);
+    assertFailure();
+  }
+
+  function assertPendingScenario() {
+    assertPartialOutput("1 scenario (1 pending)", lastRunOutput);
+    assertSuccess();
+  }
+
+  function assertUndefinedScenario() {
+    assertPartialOutput("1 scenario (1 undefined)", lastRunOutput);
+    assertSuccess();
+  }
+
+  function assertSkippedStep(stepName) {
+    if (isStepTouched(stepName))
+      throw("Expected step \"" + stepName + "\" to have been skipped.");
+  }
+
+  function assertSuccess() {
+    if (!lastRunSucceeded)
+      throw("Expected Cucumber to succeed but it failed.");
+  }
+
+  function assertFailure() {
+    if (lastRunSucceeded)
+      throw("Expected Cucumber to fail but it succeeded.");
+  }
+
+  function assertPartialOutput(expected, actual) {
+    if (actual.indexOf(expected) < 0)
+      throw("Expected:\n\"" + actual + "\"\nto match:\n\"" + expected + "\"");
+  }
+
+  function assertNoPartialOutput(expected, actual) {
+    if (actual.indexOf(expected) >= 0)
+      throw("Expected:\n\"" + actual + "\"\nnot to match:\n\"" + expected + "\"");
+  }
 };
 module.exports = cucumberSteps;
diff --git a/lib/cucumber/debug.js b/lib/cucumber/debug.js
index 7a2a30b35..f0e664cd8 100644
--- a/lib/cucumber/debug.js
+++ b/lib/cucumber/debug.js
@@ -1,7 +1,36 @@
 var Debug = {
-  TODO: function(description) {
+  TODO: function TODO(description) {
     return function() { throw("IMPLEMENT ME: " + description); };
+  },
+
+  warn: function warn(string, caption, level) {
+    if (Debug.isMessageLeveltoBeDisplayed(level))
+      process.stdout.write(Debug.warningString(string, caption));
+  },
+
+  notice: function notice(string, caption, level) {
+    if (Debug.isMessageLeveltoBeDisplayed(level))
+      process.stdout.write(Debug.noticeString(string, caption));
+  },
+
+  warningString: function warningString(string, caption) {
+    caption = caption || 'debug-warning';
+    return "\033[30;43m" + caption + ":\033[0m \033[33m" + string + "\033[0m"
+  },
+
+  noticeString: function noticeString(string, caption) {
+    caption = caption || 'debug-notice';
+    return "\033[30;46m" + caption + ":\033[0m \033[36m" + string + "\033[0m"
+  },
+
+  prefix: function prefix() {
+    return ;
+  },
+
+  isMessageLeveltoBeDisplayed: function isMessageLeveltoBeDisplayed(level) {
+    level = level || 3; // default level
+    return (level <= process.env['DEBUG_LEVEL']);
   }
 };
 Debug.SimpleAstListener = require('./debug/simple_ast_listener');
-module.exports          = Debug;
\ No newline at end of file
+module.exports          = Debug;
diff --git a/lib/cucumber/support_code/step_definition.js b/lib/cucumber/support_code/step_definition.js
index 7284ca5ba..394de721c 100644
--- a/lib/cucumber/support_code/step_definition.js
+++ b/lib/cucumber/support_code/step_definition.js
@@ -19,6 +19,8 @@ var StepDefinition = function(regexp, code) {
       try {
         code.apply(undefined, parameters);
       } catch (err) {
+        if (err)
+          Cucumber.Debug.warn(err, 'exception inside feature', 3);
         var stepResult = (err instanceof Cucumber.Runtime.PendingStepException) ?
           Cucumber.Runtime.PendingStepResult() :
           Cucumber.Runtime.FailedStepResult();