1 files changed, 161 insertions, 0 deletions
diff --git a/comm/mail/test/browser/shared-modules/MockObjectHelpers.jsm b/comm/mail/test/browser/shared-modules/MockObjectHelpers.jsm
new file mode 100644
index 0000000000..3b4ed91e53
--- /dev/null
+++ b/comm/mail/test/browser/shared-modules/MockObjectHelpers.jsm
@@ -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";
+
+const EXPORTED_SYMBOLS = ["MockObjectReplacer", "MockObjectRegisterer"];
+
+var Cm = Components.manager;
+
+function MockObjectRegisterer(aContractID, aCID, aComponent) {
+  this._contractID = aContractID;
+  this._cid = Components.ID("{" + aCID + "}");
+  this._component = aComponent;
+}
+
+MockObjectRegisterer.prototype = {
+  register() {
+    let providedConstructor = this._component;
+    this._mockFactory = {
+      createInstance(aIid) {
+        return new providedConstructor().QueryInterface(aIid);
+      },
+    };
+
+    let componentRegistrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+
+    componentRegistrar.registerFactory(
+      this._cid,
+      "",
+      this._contractID,
+      this._mockFactory
+    );
+  },
+
+  unregister() {
+    let componentRegistrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+
+    componentRegistrar.unregisterFactory(this._cid, this._mockFactory);
+  },
+};
+
+/**
+ * Allows registering a mock XPCOM component, that temporarily replaces the
+ *  original one when an object implementing a given ContractID is requested
+ *  using createInstance.
+ *
+ * @param aContractID
+ *        The ContractID of the component to replace, for example
+ *        "@mozilla.org/filepicker;1".
+ *
+ * @param aReplacementCtor
+ *        The constructor function for the JavaScript object that will be
+ *        created every time createInstance is called. This object must
+ *        implement QueryInterface and provide the XPCOM interfaces required by
+ *        the specified ContractID (for example
+ *        Ci.nsIFilePicker).
+ */
+
+function MockObjectReplacer(aContractID, aReplacementCtor) {
+  this._contractID = aContractID;
+  this._replacementCtor = aReplacementCtor;
+  this._cid = null;
+}
+
+MockObjectReplacer.prototype = {
+  /**
+   * Replaces the current factory with one that returns a new mock object.
+   *
+   * After register() has been called, it is mandatory to call unregister() to
+   * restore the original component. Usually, you should use a try-catch block
+   * to ensure that unregister() is called.
+   */
+  register() {
+    if (this._cid) {
+      throw Error("Invalid object state when calling register()");
+    }
+
+    // Define a factory that creates a new object using the given constructor.
+    var providedConstructor = this._replacementCtor;
+    this._mockFactory = {
+      createInstance(aIid) {
+        return new providedConstructor().QueryInterface(aIid);
+      },
+    };
+
+    var retVal = swapFactoryRegistration(
+      this._cid,
+      this._originalCID,
+      this._contractID,
+      this._mockFactory
+    );
+    if ("error" in retVal) {
+      throw new Error("ERROR: " + retVal.error);
+    } else {
+      this._cid = retVal.cid;
+      this._originalCID = retVal.originalCID;
+    }
+  },
+
+  /**
+   * Restores the original factory.
+   */
+  unregister() {
+    if (!this._cid) {
+      throw Error("Invalid object state when calling unregister()");
+    }
+
+    // Free references to the mock factory.
+    swapFactoryRegistration(
+      this._cid,
+      this._originalCID,
+      this._contractID,
+      this._mockFactory
+    );
+
+    // Allow registering a mock factory again later.
+    this._cid = null;
+    this._originalCID = null;
+    this._mockFactory = null;
+  },
+
+  // --- Private methods and properties ---
+
+  /**
+   * The CID under which the mock contractID was registered.
+   */
+  _cid: null,
+
+  /**
+   * The nsIFactory that was automatically generated by this object.
+   */
+  _mockFactory: null,
+};
+
+/**
+ * Swiped from mozilla/testing/mochitest/tests/SimpleTest/specialpowersAPI.js
+ */
+function swapFactoryRegistration(CID, originalCID, contractID, newFactory) {
+  let componentRegistrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+
+  if (originalCID == null) {
+    if (contractID != null) {
+      originalCID = componentRegistrar.contractIDToCID(contractID);
+      void Cm.getClassObject(Cc[contractID], Ci.nsIFactory);
+    } else {
+      return {
+        error: "trying to register a new contract ID: Missing contractID",
+      };
+    }
+    CID = Services.uuid.generateUUID();
+
+    componentRegistrar.registerFactory(CID, "", contractID, newFactory);
+  } else {
+    componentRegistrar.unregisterFactory(CID, newFactory);
+    // Restore the original factory.
+    componentRegistrar.registerFactory(originalCID, "", contractID, null);
+  }
+
+  return { cid: CID, originalCID };
+}