/toolkit/content/tests/browser/common/mockObjects.js

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 14 * The Original Code is Mozilla XUL Toolkit Testing Code.
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 16 * The Initial Developer of the Original Code is
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 36
 37/**
 38 * Allows registering a mock XPCOM component, that temporarily replaces the
 39 *  original one when an object implementing a given ContractID is requested
 40 *  using createInstance.
 41 *
 42 * @param aContractID
 43 *        The ContractID of the component to replace, for example
 44 *        "@mozilla.org/filepicker;1".
 45 *
 46 * @param aReplacementCtor
 47 *        The constructor function for the JavaScript object that will be
 48 *        created every time createInstance is called. This object must
 49 *        implement QueryInterface and provide the XPCOM interfaces required by
 50 *        the specified ContractID (for example
 51 *        Components.interfaces.nsIFilePicker).
 52 */
 53
 54function MockObjectRegisterer(aContractID, aReplacementCtor) {
 55  this._contractID = aContractID;
 56  this._replacementCtor = aReplacementCtor;
 57}
 58
 59MockObjectRegisterer.prototype = {
 60  /**
 61   * Replaces the current factory with one that returns a new mock object.
 62   *
 63   * After register() has been called, it is mandatory to call unregister() to
 64   * restore the original component. Usually, you should use a try-catch block
 65   * to ensure that unregister() is called.
 66   */
 67  register: function MOR_register() {
 68    if (this._originalFactory)
 69      throw new Exception("Invalid object state when calling register()");
 70
 71    // Define a factory that creates a new object using the given constructor.
 72    var providedConstructor = this._replacementCtor;
 73    this._mockFactory = {
 74      createInstance: function MF_createInstance(aOuter, aIid) {
 75        if (aOuter != null)
 76          throw Components.results.NS_ERROR_NO_AGGREGATION;
 77        return new providedConstructor().QueryInterface(aIid);
 78      }
 79    };
 80
 81    var retVal = SpecialPowers.swapFactoryRegistration(this._cid, this._contractID, this._mockFactory, this._originalFactory);
 82    if ('error' in retVal) {
 83      throw new Exception("ERROR: " + retVal.error);
 84    } else {
 85      this._cid = retVal.cid;
 86      this._originalFactory = retVal.originalFactory;
 87    }
 88  },
 89
 90  /**
 91   * Restores the original factory.
 92   */
 93  unregister: function MOR_unregister() {
 94    if (!this._originalFactory)
 95      throw new Exception("Invalid object state when calling unregister()");
 96
 97    // Free references to the mock factory.
 98    SpecialPowers.swapFactoryRegistration(this._cid, this._contractID, this._mockFactory, this._originalFactory);
 99
100    // Allow registering a mock factory again later.
101    this._cid = null;
102    this._originalFactory = null;
103    this._mockFactory = null;
104  },
105
106  // --- Private methods and properties ---
107
108  /**
109   * The factory of the component being replaced.
110   */
111  _originalFactory: null,
112
113  /**
114   * The CID under which the mock contractID was registered.
115   */
116  _cid: null,
117
118  /**
119   * The nsIFactory that was automatically generated by this object.
120   */
121  _mockFactory: null
122}