Testing window.document:
selectorText initial value: .green-background
container element backgroundColor initial value: rgb(255, 0, 0)
selectorText after setting selectorText value to #container: #container
container element backgroundColor after setting selectorText value to #container: rgb(0, 255, 0)
Testing iframe.contentDocument:
selectorText initial value: .green-background
container element backgroundColor initial value: rgb(255, 0, 0)
selectorText after setting selectorText value to #container: #container
container element backgroundColor after setting selectorText value to #container: rgb(0, 255, 0)
