[Files app] Added a unit test

Change-Id: I3e22e420bd7281dae51cbc7432712a60d6b608ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626057
Commit-Queue: François Degros <fdegros@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Auto-Submit: François Degros <fdegros@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662517}

ui/file_manager/base/js/test_error_reporting.js

@@ -2,6 +2,23 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+/**
+ * Asserts that promise gets rejected.
+ * @param {Promise} promise
+ */
+async function assertRejected(promise) {
+  let triggeredError = false;
+  try {
+    await promise;
+  } catch (e) {
+    triggeredError = true;
+  }
+
+  if (!triggeredError) {
+    throw new Error('Assertion Failed: Expected promise to be rejected');
+  }
+}
+
 /**
  * Invokes a callback function depending on the result of promise.
  *

ui/file_manager/file_manager/background/js/volume_manager_unittest.js

@@ -425,3 +425,11 @@ function testDriveMountedDuringInitialization(callback) {
 
   reportPromise(test(), callback);
 }
+
+function testErrorPropagatedDuringInitialization(done) {
+  chrome.fileManagerPrivate.getVolumeMetadataList = () => {
+    throw new Error('Dummy error for test purpose');
+  };
+
+  reportPromise(assertRejected(volumeManagerFactory.getInstance()), done);
+}