Tests that adding an invalid property retains its syntax.

Text
Before append:
[expanded] 
element.style  { ()
font-size: 12px;

[expanded] 
div  { (user agent stylesheet)
display: block;


After append:
[expanded] 
element.style  { ()
font-size: 12px;

[expanded] 
div  { (user agent stylesheet)
display: block;