fix test

IPython/html/tests/widgets/widget_button.js

@@ -1,45 +1,47 b''
 // Test widget button class
 casper.notebook_test(function () {
     var button_index = this.append_cell(
         'from IPython.html import widgets\n' + 
         'from IPython.display import display, clear_output\n' +
         'button = widgets.Button(description="Title")\n' +
         'display(button)\n' +
         'print("Success")\n' +
         'def handle_click(sender):\n' +
         '    display("Clicked")\n' +
         'button.on_click(handle_click)');
     this.execute_cell_then(button_index, function(index){
         this.test.assertEquals(this.get_output_cell(index).text, 'Success\n',
             'Create button cell executed with correct output.');
     });
 
     // Wait for the widgets to actually display.
     var widget_button_selector = '.widget-area .widget-subarea button';
     this.wait_for_element(button_index, widget_button_selector);
 
     // Continue with the tests.
     this.then(function() {
         this.test.assert(this.cell_element_exists(button_index, 
             '.widget-area .widget-subarea'),
             'Widget subarea exists.');
 
         this.test.assert(this.cell_element_exists(button_index, 
             widget_button_selector),
             'Widget button exists.');
 
         this.test.assert(this.cell_element_function(button_index, 
             widget_button_selector, 'html')=='Title',
             'Set button description.');
 
         this.cell_element_function(button_index, 
             widget_button_selector, 'click');
     });
 
     this.wait_for_output(button_index, 1);
 
     this.then(function () {
-        this.test.assertEquals(this.get_output_cell(button_index, 1).data['text/plain'], "'Clicked'",
+        this.test.assertEquals(this.get_output_cell(button_index, 1).text, "WARNING: The widget API is still considered experimental and \n    may change by the next major release of IPython.\n",
+            'Importing widgets show a warning');
+        this.test.assertEquals(this.get_output_cell(button_index, 2).data['text/plain'], "'Clicked'",
             'Button click event fires.');
     });
-});
  No newline at end of file
+});