Tests that WebInspector.CSSStyleSheet methods work as expected. Inspect Me Running: testSetText === Original stylesheet text: === body { font-size: 12px; foo: bar ! important /* !important property not recognized by WebCore */; height: 100% !important; colorz: "!important"; important:!important; color: "badcolor" ! important /* good property with strange value */; } @media { /* @media rule with an empty media list */ } /* comment before selector */body.main1/* comment after selector */{/* comment */color: #F00BAA;zoo:moo /* not an !important unrecognized property */}/* comment */ body.main2{background: green /* value !important comment */ !important /* no semicolon, very !important */} Running: testNewElementStyles === Matched rules for h1 after setText() === rule h1: [user-agent] ['display':'block'] @[undefined-undefined] style ['font-size':'2em'] @[undefined-undefined] style ['-webkit-margin-before':'0.67em'] @[undefined-undefined] style ['-webkit-margin-after':'0.67em'] @[undefined-undefined] style ['-webkit-margin-start':'0px'] @[undefined-undefined] style ['-webkit-margin-end':'0px'] @[undefined-undefined] style ['font-weight':'bold'] @[undefined-undefined] style rule h1: [regular] ['COLOR':'Red'] @[0:5-0:16] active