Merge pull request #6920 from SylvainCorlay/serialize_date

Dates and Strings are JavaScript objects, and _pack_models behaves incorrectly in these cases.

IPython/html/static/widgets/js/widget.js

@@ -1,621 +1,622 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define(["widgets/js/manager",
         "underscore",
         "backbone", 
         "jquery",   
         "base/js/namespace",
 ], function(widgetmanager, _, Backbone, $, IPython){
 
     var WidgetModel = Backbone.Model.extend({
         constructor: function (widget_manager, model_id, comm, init_state_callback) {
             // Constructor
             //
             // Creates a WidgetModel instance.
             //
             // Parameters
             // ----------
             // widget_manager : WidgetManager instance
             // model_id : string
             //      An ID unique to this model.
             // comm : Comm instance (optional)
             // init_state_callback : callback (optional)
             //      Called once when the first state message is recieved from 
             //      the back-end.
             this.widget_manager = widget_manager;
             this.init_state_callback = init_state_callback;
             this._buffered_state_diff = {};
             this.pending_msgs = 0;
             this.msg_buffer = null;
             this.state_lock = null;
             this.id = model_id;
             this.views = {};
 
             if (comm !== undefined) {
                 // Remember comm associated with the model.
                 this.comm = comm;
                 comm.model = this;
 
                 // Hook comm messages up to model.
                 comm.on_close($.proxy(this._handle_comm_closed, this));
                 comm.on_msg($.proxy(this._handle_comm_msg, this));
             }
             return Backbone.Model.apply(this);
         },
 
         send: function (content, callbacks) {
             // Send a custom msg over the comm.
             if (this.comm !== undefined) {
                 var data = {method: 'custom', content: content};
                 this.comm.send(data, callbacks);
                 this.pending_msgs++;
             }
         },
 
         _handle_comm_closed: function (msg) {
             // Handle when a widget is closed.
             this.trigger('comm:close');
             this.stopListening();
             this.trigger('destroy', this);
             delete this.comm.model; // Delete ref so GC will collect widget model.
             delete this.comm;
             delete this.model_id; // Delete id from model so widget manager cleans up.
             for (var id in this.views) {
                 if (this.views.hasOwnProperty(id)) {
                     this.views[id].remove();
                 }
             }
         },
 
         _handle_comm_msg: function (msg) {
             // Handle incoming comm msg.
             var method = msg.content.data.method;
             switch (method) {
                 case 'update':
                     this.set_state(msg.content.data.state);
                     if (this.init_state_callback) {
                         this.init_state_callback.apply(this, [this]);
                         delete this.init_state_callback;
                     }
                     break;
                 case 'custom':
                     this.trigger('msg:custom', msg.content.data.content);
                     break;
                 case 'display':
                     this.widget_manager.display_view(msg, this);
                     break;
             }
         },
 
         set_state: function (state) {
             // Handle when a widget is updated via the python side.
             this.state_lock = state;
             try {
                 var that = this;
                 WidgetModel.__super__.set.apply(this, [Object.keys(state).reduce(function(obj, key) {
                     obj[key] = that._unpack_models(state[key]);
                     return obj;
                 }, {})]);
             } finally {
                this.state_lock = null;
             }
         },
 
         _handle_status: function (msg, callbacks) {
             // Handle status msgs.
 
             // execution_state : ('busy', 'idle', 'starting')
             if (this.comm !== undefined) {
                 if (msg.content.execution_state ==='idle') {
                     // Send buffer if this message caused another message to be
                     // throttled.
                     if (this.msg_buffer !== null &&
                         (this.get('msg_throttle') || 3) === this.pending_msgs) {
                         var data = {method: 'backbone', sync_method: 'update', sync_data: this.msg_buffer};
                         this.comm.send(data, callbacks);
                         this.msg_buffer = null;
                     } else {
                         --this.pending_msgs;
                     }
                 }
             }
         },
 
         callbacks: function(view) {
             // Create msg callbacks for a comm msg.
             var callbacks = this.widget_manager.callbacks(view);
 
             if (callbacks.iopub === undefined) {
                 callbacks.iopub = {};
             }
 
             var that = this;
             callbacks.iopub.status = function (msg) {
                 that._handle_status(msg, callbacks);
             };
             return callbacks;
         },
 
         set: function(key, val, options) {
             // Set a value.
             var return_value = WidgetModel.__super__.set.apply(this, arguments);
 
             // Backbone only remembers the diff of the most recent set()
             // operation.  Calling set multiple times in a row results in a 
             // loss of diff information.  Here we keep our own running diff.
             this._buffered_state_diff = $.extend(this._buffered_state_diff, this.changedAttributes() || {});
             return return_value;
         },
 
         sync: function (method, model, options) {
             // Handle sync to the back-end.  Called when a model.save() is called.
 
             // Make sure a comm exists.
             var error = options.error || function() {
                 console.error('Backbone sync error:', arguments);
             };
             if (this.comm === undefined) {
                 error();
                 return false;
             }
 
             // Delete any key value pairs that the back-end already knows about.
             var attrs = (method === 'patch') ? options.attrs : model.toJSON(options);
             if (this.state_lock !== null) {
                 var keys = Object.keys(this.state_lock);
                 for (var i=0; i<keys.length; i++) {
                     var key = keys[i];
                     if (attrs[key] === this.state_lock[key]) {
                         delete attrs[key];
                     }
                 }
             }
 
             // Only sync if there are attributes to send to the back-end.
             attrs = this._pack_models(attrs);
             if (_.size(attrs) > 0) {
 
                 // If this message was sent via backbone itself, it will not
                 // have any callbacks.  It's important that we create callbacks
                 // so we can listen for status messages, etc...
                 var callbacks = options.callbacks || this.callbacks();
 
                 // Check throttle.
                 if (this.pending_msgs >= (this.get('msg_throttle') || 3)) {
                     // The throttle has been exceeded, buffer the current msg so
                     // it can be sent once the kernel has finished processing 
                     // some of the existing messages.
                     
                     // Combine updates if it is a 'patch' sync, otherwise replace updates
                     switch (method) {
                         case 'patch':
                             this.msg_buffer = $.extend(this.msg_buffer || {}, attrs);
                             break;
                         case 'update':
                         case 'create':
                             this.msg_buffer = attrs;
                             break;
                         default:
                             error();
                             return false;
                     }
                     this.msg_buffer_callbacks = callbacks;
 
                 } else {
                     // We haven't exceeded the throttle, send the message like 
                     // normal.
                     var data = {method: 'backbone', sync_data: attrs};
                     this.comm.send(data, callbacks);
                     this.pending_msgs++;
                 }
             }
             // Since the comm is a one-way communication, assume the message 
             // arrived.  Don't call success since we don't have a model back from the server
             // this means we miss out on the 'sync' event.
             this._buffered_state_diff = {};
         },
 
         save_changes: function(callbacks) {
             // Push this model's state to the back-end
             //
             // This invokes a Backbone.Sync.
             this.save(this._buffered_state_diff, {patch: true, callbacks: callbacks});
         },
 
         _pack_models: function(value) {
             // Replace models with model ids recursively.
             var that = this;
             var packed;
             if (value instanceof Backbone.Model) {
                 return "IPY_MODEL_" + value.id;
 
             } else if ($.isArray(value)) {
                 packed = [];
                 _.each(value, function(sub_value, key) {
                     packed.push(that._pack_models(sub_value));
                 });
                 return packed;
-
+            } else if (value instanceof Date || value instanceof String) {
+                return value;
             } else if (value instanceof Object) {
                 packed = {};
                 _.each(value, function(sub_value, key) {
                     packed[key] = that._pack_models(sub_value);
                 });
                 return packed;
 
             } else {
                 return value;
             }
         },
 
         _unpack_models: function(value) {
             // Replace model ids with models recursively.
             var that = this;
             var unpacked;
             if ($.isArray(value)) {
                 unpacked = [];
                 _.each(value, function(sub_value, key) {
                     unpacked.push(that._unpack_models(sub_value));
                 });
                 return unpacked;
 
             } else if (value instanceof Object) {
                 unpacked = {};
                 _.each(value, function(sub_value, key) {
                     unpacked[key] = that._unpack_models(sub_value);
                 });
                 return unpacked;
 
             } else if (typeof value === 'string' && value.slice(0,10) === "IPY_MODEL_") {
                 var model = this.widget_manager.get_model(value.slice(10, value.length));
                 if (model) {
                     return model;
                 } else {
                     return value;
                 }
             } else {
                     return value;
             }
         },
 
         on_some_change: function(keys, callback, context) {
             // on_some_change(["key1", "key2"], foo, context) differs from
             // on("change:key1 change:key2", foo, context).
             // If the widget attributes key1 and key2 are both modified, 
             // the second form will result in foo being called twice
             // while the first will call foo only once.
             this.on('change', function() {
                 if (keys.some(this.hasChanged, this)) {
                     callback.apply(context);
                 }
             }, this);
 
        },
     });
     widgetmanager.WidgetManager.register_widget_model('WidgetModel', WidgetModel);
 
 
     var WidgetView = Backbone.View.extend({
         initialize: function(parameters) {
             // Public constructor.
             this.model.on('change',this.update,this);
             this.options = parameters.options;
             this.child_model_views = {};
             this.child_views = {};
             this.id = this.id || IPython.utils.uuid();
             this.model.views[this.id] = this;
             this.on('displayed', function() { 
                 this.is_displayed = true; 
             }, this);
         },
 
         update: function(){
             // Triggered on model change.
             //
             // Update view to be consistent with this.model
         },
 
         create_child_view: function(child_model, options) {
             // Create and return a child view.
             //
             // -given a model and (optionally) a view name if the view name is 
             // not given, it defaults to the model's default view attribute.
         
             // TODO: this is hacky, and makes the view depend on this cell attribute and widget manager behavior
             // it would be great to have the widget manager add the cell metadata
             // to the subview without having to add it here.
             var that = this;
             var old_callback = options.callback || function(view) {};
             options = $.extend({ parent: this, success: function(child_view) {
                 // Associate the view id with the model id.
                 if (that.child_model_views[child_model.id] === undefined) {
                     that.child_model_views[child_model.id] = [];
                 }
                 that.child_model_views[child_model.id].push(child_view.id);
 
                 // Remember the view by id.
                 that.child_views[child_view.id] = child_view;
                 old_callback(child_view);
              }}, options || {});
             
             this.model.widget_manager.create_view(child_model, options);
         },
 
         pop_child_view: function(child_model) {
             // Delete a child view that was previously created using create_child_view.
             var view_ids = this.child_model_views[child_model.id];
             if (view_ids !== undefined) {
 
                 // Only delete the first view in the list.
                 var view_id = view_ids[0];
                 var view = this.child_views[view_id];
                 delete this.child_views[view_id];
                 view_ids.splice(0,1);
                 delete child_model.views[view_id];
             
                 // Remove the view list specific to this model if it is empty.
                 if (view_ids.length === 0) {
                     delete this.child_model_views[child_model.id];
                 }
                 return view;
             }
             return null;
         },
 
         do_diff: function(old_list, new_list, removed_callback, added_callback) {
             // Difference a changed list and call remove and add callbacks for 
             // each removed and added item in the new list.
             //
             // Parameters
             // ----------
             // old_list : array
             // new_list : array
             // removed_callback : Callback(item)
             //      Callback that is called for each item removed.
             // added_callback : Callback(item)
             //      Callback that is called for each item added.
 
             // Walk the lists until an unequal entry is found.
             var i;
             for (i = 0; i < new_list.length; i++) {
                 if (i >= old_list.length || new_list[i] !== old_list[i]) {
                     break;
                 }
             }
 
             // Remove the non-matching items from the old list.
             for (var j = i; j < old_list.length; j++) {
                 removed_callback(old_list[j]);
             }
 
             // Add the rest of the new list items.
             for (; i < new_list.length; i++) {
                 added_callback(new_list[i]);
             }
         },
 
         callbacks: function(){
             // Create msg callbacks for a comm msg.
             return this.model.callbacks(this);
         },
 
         render: function(){
             // Render the view.
             //
             // By default, this is only called the first time the view is created
         },
 
         show: function(){
             // Show the widget-area
             if (this.options && this.options.cell &&
                 this.options.cell.widget_area !== undefined) {
                 this.options.cell.widget_area.show();
             }
         },
 
         send: function (content) {
             // Send a custom msg associated with this view.
             this.model.send(content, this.callbacks());
         },
 
         touch: function () {
             this.model.save_changes(this.callbacks());
         },
 
         after_displayed: function (callback, context) {
             // Calls the callback right away is the view is already displayed
             // otherwise, register the callback to the 'displayed' event.
             if (this.is_displayed) {
                 callback.apply(context);
             } else {
                 this.on('displayed', callback, context);
             }
         },
     });
 
 
     var DOMWidgetView = WidgetView.extend({
         initialize: function (parameters) {
             // Public constructor
             DOMWidgetView.__super__.initialize.apply(this, [parameters]);
             this.on('displayed', this.show, this);
             this.model.on('change:visible', this.update_visible, this);
             this.model.on('change:_css', this.update_css, this);
 
             this.model.on('change:_dom_classes', function(model, new_classes) {
                 var old_classes = model.previous('_dom_classes');
                 this.update_classes(old_classes, new_classes);
             }, this);
 
             this.model.on('change:color', function (model, value) { 
                 this.update_attr('color', value); }, this);
 
             this.model.on('change:background_color', function (model, value) { 
                 this.update_attr('background', value); }, this);
 
             this.model.on('change:width', function (model, value) { 
                 this.update_attr('width', value); }, this);
 
             this.model.on('change:height', function (model, value) { 
                 this.update_attr('height', value); }, this);
 
             this.model.on('change:border_color', function (model, value) { 
                 this.update_attr('border-color', value); }, this);
 
             this.model.on('change:border_width', function (model, value) { 
                 this.update_attr('border-width', value); }, this);
 
             this.model.on('change:border_style', function (model, value) { 
                 this.update_attr('border-style', value); }, this);
 
             this.model.on('change:font_style', function (model, value) { 
                 this.update_attr('font-style', value); }, this);
 
             this.model.on('change:font_weight', function (model, value) { 
                 this.update_attr('font-weight', value); }, this);
 
             this.model.on('change:font_size', function (model, value) { 
                 this.update_attr('font-size', this._default_px(value)); }, this);
 
             this.model.on('change:font_family', function (model, value) { 
                 this.update_attr('font-family', value); }, this);
 
             this.model.on('change:padding', function (model, value) { 
                 this.update_attr('padding', value); }, this);
 
             this.model.on('change:margin', function (model, value) { 
                 this.update_attr('margin', this._default_px(value)); }, this);
 
             this.model.on('change:border_radius', function (model, value) { 
                 this.update_attr('border-radius', this._default_px(value)); }, this);
 
             this.after_displayed(function() {
                 this.update_visible(this.model, this.model.get("visible"));
                 this.update_classes([], this.model.get('_dom_classes'));
                 
                 this.update_attr('color', this.model.get('color'));
                 this.update_attr('background', this.model.get('background_color'));
                 this.update_attr('width', this.model.get('width'));
                 this.update_attr('height', this.model.get('height'));
                 this.update_attr('border-color', this.model.get('border_color'));
                 this.update_attr('border-width', this.model.get('border_width'));
                 this.update_attr('border-style', this.model.get('border_style'));
                 this.update_attr('font-style', this.model.get('font_style'));
                 this.update_attr('font-weight', this.model.get('font_weight'));
                 this.update_attr('font-size', this.model.get('font_size'));
                 this.update_attr('font-family', this.model.get('font_family'));
                 this.update_attr('padding', this.model.get('padding'));
                 this.update_attr('margin', this.model.get('margin'));
                 this.update_attr('border-radius', this.model.get('border_radius'));
 
                 this.update_css(this.model, this.model.get("_css"));
             }, this);
         },
 
         _default_px: function(value) {
             // Makes browser interpret a numerical string as a pixel value.
             if (/^\d+\.?(\d+)?$/.test(value.trim())) {
                 return value.trim() + 'px';
             }
             return value;
         },
 
         update_attr: function(name, value) {
             // Set a css attr of the widget view.
             this.$el.css(name, value);
         },
 
         update_visible: function(model, value) {
             // Update visibility
             this.$el.toggle(value);
          },
 
         update_css: function (model, css) {
             // Update the css styling of this view.
             var e = this.$el;
             if (css === undefined) {return;}
             for (var i = 0; i < css.length; i++) {
                 // Apply the css traits to all elements that match the selector.
                 var selector = css[i][0];
                 var elements = this._get_selector_element(selector);
                 if (elements.length > 0) {
                     var trait_key = css[i][1];
                     var trait_value = css[i][2];
                     elements.css(trait_key ,trait_value);
                 }
             }
         },
 
         update_classes: function (old_classes, new_classes, $el) {
             // Update the DOM classes applied to an element, default to this.$el.
             if ($el===undefined) {
                 $el = this.$el;
             }
             this.do_diff(old_classes, new_classes, function(removed) {
                 $el.removeClass(removed);
             }, function(added) {
                 $el.addClass(added);
             });
         },
 
         update_mapped_classes: function(class_map, trait_name, previous_trait_value, $el) {
             // Update the DOM classes applied to the widget based on a single
             // trait's value.
             //
             // Given a trait value classes map, this function automatically
             // handles applying the appropriate classes to the widget element
             // and removing classes that are no longer valid.
             //
             // Parameters
             // ----------
             // class_map: dictionary
             //  Dictionary of trait values to class lists.
             //  Example:
             //      {
             //          success: ['alert', 'alert-success'],
             //          info: ['alert', 'alert-info'],
             //          warning: ['alert', 'alert-warning'],
             //          danger: ['alert', 'alert-danger']
             //      };
             // trait_name: string
             //  Name of the trait to check the value of.
             // previous_trait_value: optional string, default ''
             //  Last trait value
             // $el: optional jQuery element handle, defaults to this.$el
             //  Element that the classes are applied to.
             var key = previous_trait_value;
             if (key === undefined) {
                 key = this.model.previous(trait_name);
             }
             var old_classes = class_map[key] ? class_map[key] : [];
             key = this.model.get(trait_name);
             var new_classes = class_map[key] ? class_map[key] : [];
 
             this.update_classes(old_classes, new_classes, $el || this.$el);
         },
         
         _get_selector_element: function (selector) {
             // Get the elements via the css selector.
             var elements;
             if (!selector) {
                 elements = this.$el;
             } else {
                 elements = this.$el.find(selector).addBack(selector);
             }
             return elements;
         },
     });
 
     
     var widget = {
         'WidgetModel': WidgetModel,
         'WidgetView': WidgetView,
         'DOMWidgetView': DOMWidgetView,
     };
 
     // For backwards compatability.
     $.extend(IPython, widget);
 
     return widget;
 });

IPython/html/tests/widgets/widget.js

@@ -1,176 +1,177 b''
 var xor = function (a, b) {return !a ^ !b;}; 
 var isArray = function (a) {
     try {
         return Object.toString.call(a) === "[object Array]" || Object.toString.call(a) === "[object RuntimeArray]";
     } catch (e) {
         return Array.isArray(a);
     }
 };
 var recursive_compare = function(a, b) {
     // Recursively compare two objects.
     var same = true;
     same = same && !xor(a instanceof Object || typeof a == 'object', b instanceof Object || typeof b == 'object');
     same = same && !xor(isArray(a), isArray(b));
 
     if (same) {
         if (a instanceof Object) {
             var key;
             for (key in a) {
                 if (a.hasOwnProperty(key) && !recursive_compare(a[key], b[key])) {
                     same = false;
                     break;
                 }
             }
             for (key in b) {
                 if (b.hasOwnProperty(key) && !recursive_compare(a[key], b[key])) {
                     same = false;
                     break;
                 }
             }
         } else {
             return a === b;
         }    
     }
     
     return same;
 };
 
 // Test the widget framework.
 casper.notebook_test(function () {
     var index;
 
     index = this.append_cell(
         'from IPython.html import widgets\n' + 
         'from IPython.display import display, clear_output\n' +
         'print("Success")');
     this.execute_cell_then(index);
 
     this.then(function () {
 
         // Functions that can be used to test the packing and unpacking APIs
         var that = this;
         var test_pack = function (input) {
             var output = that.evaluate(function(input) {
                 var model = new IPython.WidgetModel(IPython.notebook.kernel.widget_manager, undefined);
                 var results = model._pack_models(input);
                 return results;
             }, {input: input});
             that.test.assert(recursive_compare(input, output), 
                 JSON.stringify(input) + ' passed through Model._pack_model unchanged');
         };
         var test_unpack = function (input) {
             var output = that.evaluate(function(input) {
                 var model = new IPython.WidgetModel(IPython.notebook.kernel.widget_manager, undefined);
                 var results = model._unpack_models(input);
                 return results;
             }, {input: input});
             that.test.assert(recursive_compare(input, output), 
                 JSON.stringify(input) + ' passed through Model._unpack_model unchanged');
         };
         var test_packing = function(input) {
             test_pack(input);
             test_unpack(input);
         };
         
         test_packing({0: 'hi', 1: 'bye'});
         test_packing(['hi', 'bye']);
         test_packing(['hi', 5]);
         test_packing(['hi', '5']);
         test_packing([1.0, 0]);
         test_packing([1.0, false]);
         test_packing([1, false]);
         test_packing([1, false, {a: 'hi'}]);
         test_packing([1, false, ['hi']]);
+        test_packing([String('hi'), Date("Thu Nov 13 2014 13:46:21 GMT-0500")])
 
         // Test multi-set, single touch code.  First create a custom widget.
         this.evaluate(function() {
             var MultiSetView = IPython.DOMWidgetView.extend({
                 render: function(){
                     this.model.set('a', 1);
                     this.model.set('b', 2);
                     this.model.set('c', 3);
                     this.touch();
                 },
             });
             IPython.WidgetManager.register_widget_view('MultiSetView', MultiSetView);
         }, {});
     });
 
     // Try creating the multiset widget, verify that sets the values correctly.
     var multiset = {};
     multiset.index = this.append_cell(
         'from IPython.utils.traitlets import Unicode, CInt\n' +
         'class MultiSetWidget(widgets.Widget):\n' +
         '    _view_name = Unicode("MultiSetView", sync=True)\n' +
         '    a = CInt(0, sync=True)\n' +
         '    b = CInt(0, sync=True)\n' +
         '    c = CInt(0, sync=True)\n' +
         '    d = CInt(-1, sync=True)\n' + // See if it sends a full state.
         '    def set_state(self, sync_data):\n' +
         '        widgets.Widget.set_state(self, sync_data)\n'+
         '        self.d = len(sync_data)\n' +
         'multiset = MultiSetWidget()\n' +
         'display(multiset)\n' +
         'print(multiset.model_id)');
     this.execute_cell_then(multiset.index, function(index) {
         multiset.model_id = this.get_output_cell(index).text.trim();
     });
 
     this.wait_for_widget(multiset);
 
     index = this.append_cell(
         'print("%d%d%d" % (multiset.a, multiset.b, multiset.c))');
     this.execute_cell_then(index, function(index) {
         this.test.assertEquals(this.get_output_cell(index).text.trim(), '123',
             'Multiple model.set calls and one view.touch update state in back-end.');
     });
 
     index = this.append_cell(
         'print("%d" % (multiset.d))');
     this.execute_cell_then(index, function(index) {
         this.test.assertEquals(this.get_output_cell(index).text.trim(), '3',
             'Multiple model.set calls sent a partial state.');
     });
 
     var textbox = {};
     throttle_index = this.append_cell(
         'import time\n' +
         'textbox = widgets.Text()\n' +
         'display(textbox)\n' +
         'textbox._dom_classes = ["my-throttle-textbox"]\n' +
         'def handle_change(name, old, new):\n' +
         '    display(len(new))\n' +
         '    time.sleep(0.5)\n' +
         'textbox.on_trait_change(handle_change, "value")\n' +
         'print(textbox.model_id)');
     this.execute_cell_then(throttle_index, function(index){
         textbox.model_id = this.get_output_cell(index).text.trim();
 
         this.test.assert(this.cell_element_exists(index, 
             '.widget-area .widget-subarea'),
             'Widget subarea exists.');
 
         this.test.assert(this.cell_element_exists(index, 
             '.my-throttle-textbox'), 'Textbox exists.');
 
         // Send 20 characters
         this.sendKeys('.my-throttle-textbox input', '....................');
     });
 
     this.wait_for_widget(textbox);
 
     this.then(function () { 
         var outputs = this.evaluate(function(i) {
             return IPython.notebook.get_cell(i).output_area.outputs;
         }, {i : throttle_index});
 
         // Only 4 outputs should have printed, but because of timing, sometimes
         // 5 outputs will print.  All we need to do is verify num outputs <= 5
         // because that is much less than 20.
         this.test.assert(outputs.length <= 5, 'Messages throttled.');
 
         // We also need to verify that the last state sent was correct.
         var last_state = outputs[outputs.length-1].data['text/plain'];
         this.test.assertEquals(last_state, "20", "Last state sent when throttling.");
     });
 });