DomStorageBrowserTest sanity check

content/test/data/dom_storage/sanity_check.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.
+
+function startTestSoon() {
+  window.setTimeout(test, 0);
+}
+
+function test() {
+  try {
+    debug('Checking window.localStorage');
+    sanityCheck(window.localStorage);
+    debug('Checking window.sessionStorage');
+    sanityCheck(window.sessionStorage);
+    done();
+  } catch(e) {
+    fail(e);
+  }
+}
+
+function sanityCheck(storage) {
+  storage.clear();
+
+  checkEqual(0, storage.length,
+             "storage.length != 0 at start");
+  checkEqual(undefined, storage.getItem("foo"),
+             "getItem('foo') != undefined prior to addition");
+  checkEqual(undefined, storage.key(0),
+             "key(0) != undefined prior to addition");
+
+  storage.setItem("foo", "bar");
+
+  checkEqual(1, storage.length,
+             "storage.length != 1 after addition");
+  checkEqual("bar", storage.getItem("foo"),
+             "getItem('foo') != 'bar' after addition");
+  checkEqual("foo", storage.key(0),
+             "key(0) != 'foo' after addition");
+
+  storage.removeItem("foo");
+
+  checkEqual(undefined, storage.getItem("foo"),
+             "getItem('foo') != undefined after removal");
+
+  storage["foo"] = "baz";
+  storage["name"] = "value";
+
+  checkEqual(2, storage.length,
+             "storage.length != 2 after 2 additions");
+  checkEqual("baz", storage["foo"],
+             "storage['foo'] != 'baz' after addition");
+  checkEqual("value", storage["name"],
+             "storage['name'] != 'value' after addition");
+
+  storage.clear();
+
+  checkEqual(0, storage.length,
+             "storage.length != 0 after clear");
+
+  try {
+    storage.setItem("tooLarge", makeLargeString((5 * 1024 * 1024) + 1));
+    throw "failed to throw execption for very large value";
+  } catch(ex) {
+    checkEqual(ex.code, 22,
+               "ex.code != 22 for attempt to store a very large value");
+  }
+}
+
+function checkEqual(lhs, rhs, errorMessage) {
+  if (lhs != rhs)

[jsbell, 2012/04/04 18:37:56]

Nit: I'd prefer the stricter !== comparison, which per the DOM Storage spec
would require comparing with null vs. undefined

[michaeln, 2012/04/04 19:03:21]

Right, some of my checkEquals should be testing against null.

+    throw errorMessage;
+}
+
+function makeLargeString(minimumSize) {
+  var x = "a large string of gibberish_";
+  while (x.length < minimumSize)

[jsbell, 2012/04/04 18:37:56]

Per dgrogan's advice to me, watch out for this style being slow on the win/mac
bots. You may want to use the Array(n).join(x) trick; I guess n would be
Math.ceil(minimumSize / x.length)

Also (based on my recent max-value-size-for-IDB-tests), if the limit is based on
byte count not character count, be paranoid about whether the strings end up
being UTF-16 or UTF-8, and it might vary per platform (leading to testing two
different sizes on win bots vs. mac/linux bots). (I ended up using a string of
"\u0100" since that encodes to the same length in both.)

[michaeln, 2012/04/04 19:03:21]

At the sizes i'm working with, i haven't noticed this being at all slow, but you
say Array().join(x) is actually faster... ok... i'll switch to doing that here.
It's all UTF-16 and values are treated like binary data in the backend.

+    x = x.concat(x);
+  return x;
+}