Added mock_xhr module w/ unit tests.

remoting/webapp/crd/js/mock_xhr.js

+/**
+ * @fileoverview A mock version of remoting.Xhr.  Compared to
+ * sinon.useMockXhr, this allows unit tests to be written at a higher
+ * level, and it eliminates a fair amount of boilerplate involved in
+ * making the sinon mocks work with asynchronous calls
+ * (cf. gcd_client_unittest.js vs. gcd_client_with_mock_xhr.js for an
+ * example).
+ */
+
+(function() {
+'use strict';
+
+/**
+ * @constructor
+ * @param {remoting.Xhr.Params} params
+ */
+remoting.MockXhr = function(params) {
+  origXhr['checkParams_'](params);
+
+  /** @const {remoting.Xhr.Params} */
+  this.params = normalizeParams(params);
+
+  /** @private {base.Deferred<!remoting.Xhr.Response>} */
+  this.deferred_ = null;
+
+  /** @type {remoting.Xhr.Response} */
+  this.response_ = null;
+
+  /** @type {boolean} */
+  this.aborted_ = false;
+};
+
+/**
+ * Converts constuctor parameters to a normalized form that hides
+ * details of how the constructor is called.
+ * @param {remoting.Xhr.Params} params
+ * @return {remoting.Xhr.Params} The argument with all missing fields
+ *     filled in with default values.
+ */
+var normalizeParams = function(params) {
+  return {
+    method: params.method,
+    url: params.url,
+    urlParams: typeof params.urlParams == 'object' ?
+        base.copyWithoutNullFields(params.urlParams) :
+        params.urlParams,
+    textContent: params.textContent,
+    jsonContent: params.jsonContent,
+    formContent: params.formContent === undefined ? undefined :
+        base.copyWithoutNullFields(params.formContent),
+    headers: base.copyWithoutNullFields(params.headers),
+    withCredentials: Boolean(params.withCredentials),
+    oauthToken: params.oauthToken,
+    useIdentity: Boolean(params.useIdentity),
+    acceptJson: Boolean(params.acceptJson)
+  };
+};
+
+/**
+ * Psuedo-override from remoting.Xhr.
+ * @return {void}
+ */
+remoting.MockXhr.prototype.abort = function() {
+  this.aborted_ = true;
+};
+
+/**
+ * Psuedo-override from remoting.Xhr.
+ * @return {!Promise<!remoting.Xhr.Response>}
+ */
+remoting.MockXhr.prototype.start = function() {
+  runMatchingHandler(this);
+  if (!this.deferred_) {
+    this.deferred_ = new base.Deferred();
+    this.maybeRespond_();
+  }
+  return this.deferred_.promise();
+};
+
+/**
+ * Tells this object to send an empty response to the current or next
+ * request.
+ * @param {number} status The HTTP status code to respond with.
+ */
+remoting.MockXhr.prototype.setEmptyResponse = function(status) {
+  this.setResponse_(new remoting.Xhr.Response(
+      status,
+      'mock status text from setEmptyResponse',
+      null,
+      '',
+      false));
+};
+
+/**
+ * Tells this object to send a text/plain response to the current or
+ * next request.
+ * @param {number} status The HTTP status code to respond with.
+ * @param {string} body The content to respond with.
+ */
+remoting.MockXhr.prototype.setTextResponse = function(status, body) {
+  this.setResponse_(new remoting.Xhr.Response(
+      status,
+      'mock status text from setTextResponse',
+      null,
+      body || '',
+      false));
+};
+
+/**
+ * Tells this object to send an application/json response to the
+ * current or next request.
+ * @param {number} status The HTTP status code to respond with.
+ * @param {*} body The content to respond with.
+ */
+remoting.MockXhr.prototype.setJsonResponse = function(status, body) {
+  if (!this.params.acceptJson) {
+    throw new Error('client does not want JSON response');
+  }
+  this.setResponse_(new remoting.Xhr.Response(
+      status,
+      'mock status text from setJsonResponse',
+      null,
+      JSON.stringify(body),
+      true));
+};
+
+/**
+ * Sets the response to be used for the current or next request.
+ * @param {!remoting.Xhr.Response} response
+ * @private
+ */
+remoting.MockXhr.prototype.setResponse_ = function(response) {
+  base.debug.assert(this.response_ == null);
+  this.response_ = response;
+  this.maybeRespond_();
+};
+
+/**
+ * Sends a response if one is available.
+ * @private
+ */
+remoting.MockXhr.prototype.maybeRespond_ = function() {
+  if (this.deferred_ && this.response_ && !this.aborted_) {
+    this.deferred_.resolve(this.response_);
+  }
+};
+
+/**
+ * The original value of the remoting.MockXhr constructor.

[Jamie, 2015/04/07 00:27:09]

s/MockXhr/Xhr/ (I think).

Also, please add something along the lines of "The JSDoc type is that of the
remoting.Xhr constructor function."

+ * @type {?function(this: remoting.Xhr, remoting.Xhr.Params):void}
+ */
+var origXhr = null;
+
+/**
+ * @type {!Array<remoting.MockXhr.UrlHandler>}
+ */
+var handlers = [];
+
+/**
+ * Registers a handler for a given method and URL.  The |urlPattern|
+ * argument may either be a string, which must equal a URL to match
+ * it, or a RegExp.
+ *
+ * Matching handlers are run when a FakeXhr's |start| method is
+ * called.  The handler should generally call one on

[Jamie, 2015/04/07 00:27:09]

s/on/of/

+ * |set{Test,Json,Empty}Response|
+ *
+ * @param {?string} method The HTTP method to respond to, or null to
+ *     respond to any method.
+ * @param {?string|!RegExp} urlPattern The URL or pattern to respond
+ *     to, or null to match any URL.
+ * @param {function(!remoting.MockXhr):void} callback The handler
+ *     function to call when a matching XHR is started.
+ * @param {boolean=} opt_reuse If true, the response can be used for
+ *     multiple requests.
+ */
+remoting.MockXhr.setResponseFor = function(
+    method, urlPattern, callback, opt_reuse) {
+  handlers.push({
+    method: method,
+    urlPattern: urlPattern,
+    callback: callback,
+    reuse: !!opt_reuse
+  });
+};
+
+/**
+ * Installs a 204 (no content) response.  See |setResponseFor| for
+ * more details on how the parameters work.
+ *
+ * @param {?string} method
+ * @param {?string|!RegExp} urlPattern
+ * @param {boolean=} opt_reuse
+ */
+remoting.MockXhr.setEmptyResponseFor = function(method, urlPattern, opt_reuse) {
+  remoting.MockXhr.setResponseFor(
+      method, urlPattern, function(/** remoting.MockXhr */ xhr) {
+        xhr.setEmptyResponse(204);
+      }, opt_reuse);
+};
+
+/**
+ * Installs a 200 response with text content.  See |setResponseFor|
+ * for more details on how the parameters work.
+ *
+ * @param {?string} method
+ * @param {?string|!RegExp} urlPattern
+ * @param {string} content
+ * @param {boolean=} opt_reuse
+ */
+remoting.MockXhr.setTextResponseFor = function(
+    method, urlPattern, content, opt_reuse) {
+  remoting.MockXhr.setResponseFor(
+      method, urlPattern, function(/** remoting.MockXhr */ xhr) {
+        xhr.setTextResponse(200, content);
+      }, opt_reuse);
+};
+
+/**
+ * Installs a 200 response with JSON content.  See |setResponseFor|
+ * for more details on how the parameters work.
+ *
+ * @param {?string} method
+ * @param {?string|!RegExp} urlPattern
+ * @param {*} content
+ * @param {boolean=} opt_reuse
+ */
+remoting.MockXhr.setJsonResponseFor = function(
+    method, urlPattern, content, opt_reuse) {
+  remoting.MockXhr.setResponseFor(
+      method, urlPattern, function(/** remoting.MockXhr */ xhr) {
+        xhr.setJsonResponse(200, content);
+      }, opt_reuse);
+};
+
+/**
+ * Runs the most first handler for a given method and URL.
+ * @param {!remoting.MockXhr} xhr
+ */
+var runMatchingHandler = function(xhr) {
+  for (var i = 0; i < handlers.length; i++) {
+    var handler = handlers[i];
+    if (handler.method == null || handler.method != xhr.params.method) {
+      continue;
+    }
+    if (handler.urlPattern == null) {
+      // Let the handler run.
+    } else if (typeof handler.urlPattern == 'string') {
+      if (xhr.params.url != handler.urlPattern) {
+        continue;
+      }
+    } else {
+      var regexp = /** @type {RegExp} */ (handler.urlPattern);
+      if (!regexp.test(xhr.params.url)) {
+        continue;
+      }
+    }
+    if (!handler.reuse) {
+      handlers.splice(i, 1);
+    }
+    handler.callback(xhr);
+    return;
+  };
+  throw new Error(
+      'No handler registered for ' + xhr.params.method +
+      ' to '+ xhr.params.url);
+};
+
+/**
+ * Activates this mock.
+ */
+remoting.MockXhr.activate = function() {
+  base.debug.assert(
+      origXhr == null,
+      'Xhr mocking already active');
+  origXhr = remoting.Xhr;
+  remoting.MockXhr.Response = remoting.Xhr.Response;
+  remoting['Xhr'] = remoting.MockXhr;
+};
+
+/**
+ * Restores the original definiton of |remoting.Xhr|.
+ */
+remoting.MockXhr.restore = function() {
+  base.debug.assert(
+      origXhr != null,
+      'Xhr mocking not active');
+  remoting['Xhr'] = origXhr;
+  origXhr = null;
+  handlers = [];
+};
+
+})();
+
+// Can't put put typedefs inside a function :-(
+/**
+ * @typedef {{
+ *   method:?string,
+ *   urlPattern:(?string|RegExp),
+ *   callback:function(!remoting.MockXhr):void,
+ *   reuse:boolean
+ * }}
+ */
+remoting.MockXhr.UrlHandler;