Added combined test for Syncable File System to write file and then get that usage gets updated.

chrome/test/data/extensions/api_test/sync_file_system/write_file_then_get_usage/test.js

+// Copyright (c) 2012 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 fileEntry;
+var usageBeforeWrite;
+var testData = "12345";
+
+var testStep = [
+  function () {
+    chrome.syncFileSystem.requestFileSystem('drive', testStep.shift());
+  },
+  // Create empty file.
+  function(fileSystem) {
+    fileSystem.root.getFile('Test.txt', {create: true}, testStep.shift(),
+        errorHandler);
+  },
+  function(entry) {
+    fileEntry = entry;
+    testStep.shift()();
+  },
+  // Record usage before write.
+  function() {
+    chrome.syncFileSystem.getUsageAndQuota('drive', testStep.shift());
+  },
+  function(storageInfo) {
+    usageBeforeWrite = storageInfo.usage_bytes;
+    testStep.shift()();
+  },
+  // Write a known number of bytes.
+  function() {
+    fileEntry.createWriter(testStep.shift(), errorHandler);
+  },
+  function (fileWriter) {
+    fileWriter.onwriteend = function(e) {
+      testStep.shift()();
+    };
+    fileWriter.onerror = function(e) {
+      chrome.test.fail('Write failed: ' + e.toString());
+    };
+    fileWriter.seek(fileWriter.length);
+    var blob = new Blob([testData], {type: "text/plain"});
+    fileWriter.write(blob);
+  },
+  // Check the meta data for updated usage.
+  function() {
+    fileEntry.getMetadata(testStep.shift(), errorHandler);
+  },
+  function (metadata) {
+    chrome.test.assertEq(testData.length, metadata.size);
+    testStep.shift()();
+  },
+  // Check global usage was updated.
+  function() {
+    chrome.syncFileSystem.getUsageAndQuota('drive', testStep.shift());
+  },
+  function(storageInfo) {
+    var usageAfterWrite = storageInfo.usage_bytes;
+    chrome.test.assertEq(testData.length, usageAfterWrite - usageBeforeWrite);
+    chrome.test.succeed();
+  }
+];
+
+function errorHandler() {
+  chrome.test.fail();
+}
+
+chrome.test.runTests([
+  chrome.test.callbackPass(testStep[0])

[benwells, 2012/11/10 10:22:56]

Why are you using chrome.test.callbackPass here, this doesn't seem to be
wrapping a callback.

I have found tests can exit early if you use callbackPass and then use other
callbacks which do not go through chrome.test. Are you sure all of your test
steps are being run?

[calvinlo, 2012/11/12 04:48:07]

Sorry Ben. I'm kinda confused. When I was playing with this last week I noticed
that some of my tests were coming back as passing even if an assertion failed
using chrome.test.assertTrue or assertEq. Even if I purposely put in
chrome.test.fail(); lines in some steps the failure message would get printed to
console but the test would still say passing.

After some confusion, I tried adding in the chrome.test.callbackPass and that
seemed to fix it. However, this morning when I tried to reproduce the strange
behavior I saw before I couldn't replicate it and now just using testStep[0] on
this line works again. 

I'm honestly no sure what happened here so either I'm nuts or my machine was in
a weird state before. Anyway, it seems to be ok now so I've removed the
chrome.test.callbackPass() here now.

+]);
+