diff -r 000000000000 -r 6474c204b198 addon-sdk/source/test/test-unload.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/test/test-unload.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,161 @@
+/* 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";
+
+var unload = require("sdk/system/unload");
+var { Loader, LoaderWithHookedConsole } = require("sdk/test/loader");
+
+exports.testUnloading = function(assert) {
+  let { loader, messages } = LoaderWithHookedConsole(module);
+  var ul = loader.require("sdk/system/unload");
+  var unloadCalled = 0;
+  function unload() {
+    unloadCalled++;
+    throw new Error("error");
+  }
+  ul.when(unload);
+
+  // This should be ignored, as we already registered it
+  ul.when(unload);
+
+  function unload2() { unloadCalled++; }
+  ul.when(unload2);
+  loader.unload();
+  assert.equal(unloadCalled, 2,
+                   "Unloader functions are called on unload.");
+  assert.equal(messages.length, 1,
+                   "One unload handler threw exception 1/2");
+  assert.equal(messages[0].type, "exception",
+                   "One unload handler threw exception 2/2");
+};
+
+exports.testEnsure = function(assert) {
+  assert.throws(function() { unload.ensure({}); },
+                /object has no 'unload' property/,
+                "passing obj with no unload prop should fail");
+  assert.throws(function() { unload.ensure({}, "destroy"); },
+                /object has no 'destroy' property/,
+                "passing obj with no custom unload prop should fail");
+
+  var called = 0;
+  var obj = {unload: function() { called++; }};
+
+  unload.ensure(obj);
+  obj.unload();
+  assert.equal(called, 1,
+                   "unload() should be called");
+  obj.unload();
+  assert.equal(called, 1,
+                   "unload() should be called only once");
+};
+
+/**
+ * Check that destructors are called only once with Traits.
+ * - check that public API is calling the destructor and unregister it,
+ * - check that composed traits with multiple ensure calls, leads to only
+ * one destructor call.
+ */
+exports.testEnsureWithTraits = function(assert) {
+  let { Trait } = require("sdk/deprecated/traits");
+  let loader = Loader(module);
+  let ul = loader.require("sdk/system/unload");
+
+  let called = 0;
+  let composedCalled = 0;
+  let composedTrait = Trait.compose({
+      constructor: function () {
+        // We have to give "public interface" of this trait, as we want to
+        // call public `unload` method and ensure that we call it only once,
+        // either when we call this public function manually or on add-on unload
+        ul.ensure(this._public);
+      },
+      unload: function unload() {
+        composedCalled++;
+      }
+    });
+  let obj = Trait.compose(
+    composedTrait.resolve({
+      constructor: "_constructor",
+      unload : "_unload"
+    }), {
+      constructor: function constructor() {
+        // Same thing applies here, we need to pass public interface
+        ul.ensure(this._public);
+        this._constructor();
+      },
+      unload: function unload() {
+        called++;
+        this._unload();
+      }
+    })();
+
+  obj.unload();
+  assert.equal(called, 1,
+                   "unload() should be called");
+
+  assert.equal(composedCalled, 1,
+                   "composed object unload() should be called");
+
+  obj.unload();
+  assert.equal(called, 1,
+                   "unload() should be called only once");
+  assert.equal(composedCalled, 1,
+                   "composed object unload() should be called only once");
+
+  loader.unload();
+  assert.equal(called, 1,
+                   "unload() should be called only once, after addon unload");
+  assert.equal(composedCalled, 1,
+                   "composed object unload() should be called only once, " +
+                   "after addon unload");
+};
+
+exports.testEnsureWithTraitsPrivate = function(assert) {
+  let { Trait } = require("sdk/deprecated/traits");
+  let loader = Loader(module);
+  let ul = loader.require("sdk/system/unload");
+
+  let called = 0;
+  let privateObj = null;
+  let obj = Trait.compose({
+      constructor: function constructor() {
+        // This time wa don't have to give public interface,
+        // as we want to call a private method:
+        ul.ensure(this, "_unload");
+        privateObj = this;
+      },
+      _unload: function unload() {
+        called++;
+        this._unload();
+      }
+    })();
+
+  loader.unload();
+  assert.equal(called, 1,
+                   "unload() should be called");
+
+  privateObj._unload();
+  assert.equal(called, 1,
+                   "_unload() should be called only once, after addon unload");
+};
+
+exports.testReason = function (assert) {
+  var reason = "Reason doesn't actually have to be anything in particular.";
+  var loader = Loader(module);
+  var ul = loader.require("sdk/system/unload");
+  ul.when(function (rsn) {
+    assert.equal(rsn, reason,
+                     "when() reason should be reason given to loader");
+  });
+  var obj = {
+    unload: function (rsn) {
+      assert.equal(rsn, reason,
+                       "ensure() reason should be reason given to loader");
+    }
+  };
+  ul.ensure(obj);
+  loader.unload(reason);
+};
+
+require("sdk/test").run(exports);