Adding unit tests for #8403

test/data/testsuite.css

 /* for testing opacity set in styles in IE */
-ol#empty { opacity: 0; filter:Alpha(opacity=0); }
+ol#empty { opacity: 0; filter:Alpha(opacity=0) progid:DXImageTransform.Microsoft.gradient(startColorStr='#ffff0000', EndColorStr='#ffffffff'); }
 
 div#fx-tests h4 {
         background: red;

test/unit/css.js

 module("css", { teardown: moduleTeardown });
 
 test("css(String|Hash)", function() {
-	expect(41);
+	expect(42);
 
 	equals( jQuery('#main').css("display"), 'block', 'Check for css property "display"');
 
@@ -58,6 +58,7 @@ test("css(String|Hash)", function() {
 	equals( jQuery('#empty').css('opacity'), '0', "Assert opacity is accessible via filter property set in stylesheet in IE" );
 	jQuery('#empty').css({ opacity: '1' });
 	equals( jQuery('#empty').css('opacity'), '1', "Assert opacity is taken from style attribute when set vs stylesheet in IE with filters" );
+	ok( ~jQuery('#empty')[0].currentStyle.filter.indexOf('gradient'), "Assert setting opacity doesn't overwrite other filters of the stylesheet in IE" );
 
 	var div = jQuery('#nothiddendiv'), child = jQuery('#nothiddendivchild');