content/base/test/chrome/test_fileconstructor.xul

<?xml version="1.0"?>
<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
<?xml-stylesheet
  href="chrome://mochikit/content/tests/SimpleTest/test.css"
  type="text/css"?>
<!--
https://bugzilla.mozilla.org/show_bug.cgi?id=607114.xul
-->
<window title="Mozilla Bug 607114"
  xmlns:html="http://www.w3.org/1999/xhtml"
  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <title>Test for Bug 607114</title>
  <script type="application/javascript"
    src="chrome://mochikit/content/MochiKit/packed.js"></script>
  <script type="application/javascript"
    src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>

<body  xmlns="http://www.w3.org/1999/xhtml">
<a target="_blank"
   href="https://bugzilla.mozilla.org/show_bug.cgi?id=607114">
   Mozilla Bug 607114</a>
<p id="display"></p>
<div id="content" style="display: none">

</div>
<pre id="test">
</pre>
</body>

<script class="testbody" type="application/javascript">
<![CDATA[

/** Test for Bug 607114 **/

var file = Components.classes["@mozilla.org/file/directory_service;1"]
           .getService(Components.interfaces.nsIProperties)
           .get("CurWorkD", Components.interfaces.nsIFile);

// man I wish this were simpler ...
file.append("chrome");
file.append("content");
file.append("base");
file.append("test");
file.append("chrome");
file.append("fileconstructor_file.png");

doTest(new File(file.path));
doTest(new File(file));
function doTest(domfile) {
  ok(domfile instanceof File, "File() should return a File");
  is(domfile.type, "image/png", "File should be a PNG");
  is(domfile.size, 95, "File has size 95 (and more importantly we can read it)");
}

try {
  var boomfile = new File();
  ok(false, "This should never be reached!");
} catch (e) {
  ok(true, "Botched file constructor attempts throw and do not crash.");
}

try {
  var nonexistentfile = new File("i/sure/hope/this/does/not/exist/anywhere.txt");
  ok(false, "This should never be reached!");
} catch (e) {
  ok(true, "Attempt to construct a non-existent file should fail.")
}

]]>
</script>

</window>