1. Run the unit tests, particularly lib/tests/outputlib_test.php 2. Copy the following code into a test script in the root of your Moodle directory: <?php require_once('config.php'); $PAGE->set_context(context_system::instance()); $PAGE->set_url('/'); echo $OUTPUT->pix_icon('i/test', 'You should never see this'); 3. Test this code in all of the supported browsers. In IE8 (or any earlier version) you should get a blue ball. In all other browsers you should get an orange ball. 4. Test the order of image caching Using IE8: Turn off theme designer mode. Purge the site caches Visit the test script and make sure you see a blue ball. Switch to Firefox or Chrome Visit the test script and check you see an orange ball. Switch back to IE8 Enable theme designer mode Visit the test script and make sure you see a blue ball. Switch to Firefox or Chrome Visit the test script and check you see an orange ball. 5. Test CSS Edit theme/base/styles/admin.css Add the following to the bottom: #sams-svg-test {background-image:url([[pix:core|i/test]]);} Using Firefox or Chrome Purge your caches Using the dev toolkit (firebug or dev tools) find the admin CSS file contents. If you have theme designer mode on it will be a separate sheet, otherwise it will be a sheet called all. Search the CSS for #sams-svg-test Check that the URL either contains /_s/ if theme designer mode off or svg=0 if theme designer mode is on.