Files.app: Create unit tests for MetadataCache.

chrome/test/data/file_manager/unit_tests/metadata_cache_unittest.js

+// Copyright 2013 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.
+
+var metadataCache;
+var provider;
+
+/**
+ * Mock of MetadataProvider.
+ * @constructor
+ */
+function MockProvider() {
+  MetadataProvider.call(this);
+  this.callbackPool = [];
+  Object.freeze(this);
+}
+
+MockProvider.prototype = {
+  __proto__: MetadataProvider.prototype
+};
+
+MockProvider.prototype.supportsEntry = function(entry) {
+  return true;
+};
+
+MockProvider.prototype.providesType = function(type) {
+  return type === 'stub';
+};
+
+MockProvider.prototype.getId = function() {
+  return 'stub';
+};
+
+MockProvider.prototype.fetch = function(entry, type, callback) {
+  this.callbackPool.push(callback);
+};
+
+/**
+ * Short hand for the metadataCache.get.
+ *
+ * @param {Array.<Entry>} entries Entries.
+ * @param {string} type Metadata type.
+ * @return {Promise} Promise to be fulfilled with the result metadata.
+ */
+function getMetadata(entries, type) {
+  return new Promise(metadataCache.get.bind(metadataCache, entries, type));
+};
+
+/**
+ * Invokes a callback function depending on the result of promise.
+ *
+ * @param {Promise} promise Promise.
+ * @param {function(boolean)} calllback Callback function. True is passed if the
+ * test failed.
+ */
+function reportPromise(promise, callback) {
+  promise.then(function() {
+    callback(/* error */ false);
+  }, function(error) {
+    console.error(error.stack || error);
+    callback(/* error */ true);
+  });
+}
+
+/**
+ * Constructs the metadata cache and its provider.
+ */
+function setUp() {
+  provider = new MockProvider();
+  metadataCache = new MetadataCache([provider]);
+}
+
+/**
+ * Confirms metadata is cached for the same entry.
+ *
+ * @param {function(boolean=)} callback Callback to be called when test
+ *     completes. If the test fails, true is passed to the function.
+ */
+function testCached(callback) {
+  var entry = new MockFileEntry('volumeId', '/banjo.txt');
+
+  var promises = [];
+  var firstPromise = getMetadata([entry], 'stub');
+  var cachedBeforeFetchingPromise =  getMetadata([entry], 'stub');
+  provider.callbackPool[0]({stub: {value: 'banjo'}});
+  var cachedAfterFethingPromise = getMetadata([entry], 'stub');
+
+  // Provide should be called only once.
+  assertEquals(1, provider.callbackPool.length);
+
+  reportPromise(Promise.all([
+    firstPromise,
+    cachedBeforeFetchingPromise,
+    cachedAfterFethingPromise
+  ]).then(function(metadata) {
+    assertDeepEquals([{value: 'banjo'}], metadata[0]);
+    assertDeepEquals([{value: 'banjo'}], metadata[1]);
+    assertDeepEquals([{value: 'banjo'}], metadata[1]);
+  }), callback);
+}
+
+/**
+ * Confirms metadata is not cached for different entries.
+ *
+ * @param {function(boolean=)} callback Callback to be called when test
+ *     completes. If the test fails, true is passed to the function.
+ */
+function testNotCached(callback) {
+  var entry1 = new MockFileEntry('volumeId', '/banjo.txt');
+  var entry2 = new MockFileEntry('volumeId', '/fiddle.txt');
+
+  var firstPromise = getMetadata([entry1], 'stub');
+  var anotherPromise = getMetadata([entry2], 'stub');
+
+  // Provide should be called for each entry.
+  assertEquals(2, provider.callbackPool.length);
+
+  provider.callbackPool[0]({stub: {value: 'banjo'}});
+  provider.callbackPool[1]({stub: {value: 'fiddle'}});
+
+  reportPromise(Promise.all([
+    firstPromise,
+    anotherPromise
+  ]).then(function(metadata) {
+    assertDeepEquals([{value: 'banjo'}], metadata[0]);
+    assertDeepEquals([{value: 'fiddle'}], metadata[1]);
+  }), callback);
+}