MD Search Field: Properly respond to external changes to search value.

chrome/test/data/webui/cr_elements/cr_toolbar_search_field_tests.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** @fileoverview Suite of tests for cr-toolbar-search-field. */
 cr.define('cr_toolbar_search_field', function() {
   function registerTests() {
     suite('cr-toolbar-search-field', function() {
       /** @type {?CrToolbarSearchFieldElement} */
       var field = null;
@@ skipping 68 matching lines @@
         assertEquals(['foo', '', 'bar', 'baz'].join(), searches.join());
       });
 
       test('blur does not close field when a search is active', function() {
         MockInteractions.tap(field);
         simulateSearch('test');
         MockInteractions.blur(field.$.searchInput);
 
         assertTrue(field.showingSearch);
       });
+
+      test('opens when value is changed', function() {
+        // Change search value without explicity opening the field first.
+        // Similar to what happens when pasting or dragging into the input
+        // field.
+        simulateSearch('test');
+
+        assertTrue(field.hasSearchText_);

[dpapad, 2016/06/23 00:44:19]

Accessing private variables from within a test ends up testing internal state
instead of behavior. This is sub-optimal, for example imagine a future change
where the data binding
hidden$="[[!hasSearchText_]]
is removed. The test would not break, but the behavior would be broken.

So a better assertion would be the following.
assertFalse(field.$.clearSearch.hidden);
which would break if behavior is broken. You might need to call
Polymer.dom.flush() before the assertion.

[tsergeant, 2016/06/23 01:00:34]

Good point, done.

+        assertTrue(field.showingSearch);
+
+        MockInteractions.tap(field.$.clearSearch);
+        assertFalse(field.showingSearch);
+      });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });