diff -r 000000000000 -r 6474c204b198 addon-sdk/source/test/event/helpers.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/test/event/helpers.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,59 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const { on, once, off, emit, count } = require("sdk/event/core");
+
+function scenario(setup) {
+  return function(unit) {
+    return function(assert) {
+      let actual = [];
+      let input = {};
+      unit(input, function(output, events, expected, message) {
+        let result = setup(output, expected, actual);
+
+        events.forEach(function(event) emit(input, "data", event));
+
+        assert.deepEqual(actual, result, message);
+      });
+    }
+  }
+}
+
+exports.emits = scenario(function(output, expected, actual) {
+  on(output, "data", function(data) actual.push(this, data));
+
+  return expected.reduce(function($$, $) $$.concat(output, $), []);
+});
+
+exports.registerOnce = scenario(function(output, expected, actual) {
+  function listener(data) actual.push(data);
+  on(output, "data", listener);
+  on(output, "data", listener);
+  on(output, "data", listener);
+
+  return expected;
+});
+
+exports.ignoreNew = scenario(function(output, expected, actual) {
+  on(output, "data", function(data) {
+    actual.push(data + "#1");
+    on(output, "data", function(data) {
+      actual.push(data + "#2");
+    });
+  });
+
+  return expected.map(function($) $ + "#1");
+});
+
+exports.FIFO = scenario(function(target, expected, actual) {
+  on(target, "data", function($) actual.push($ + "#1"));
+  on(target, "data", function($) actual.push($ + "#2"));
+  on(target, "data", function($) actual.push($ + "#3"));
+
+  return expected.reduce(function(result, value) {
+    return result.concat(value + "#1", value + "#2", value + "#3");
+  }, []);
+});