Test calling getPropertyValue on computed styles for background-position properties.
background-position: 0;
background-position
getPropertyValue: 0px 50%
background-position-x
getPropertyValue: 0px
background-position-y
getPropertyValue: 50%
background-position: 0 0;
background-position
getPropertyValue: 0px 0px
background-position-x
getPropertyValue: 0px
background-position-y
getPropertyValue: 0px
background-position: 15px;
background-position
getPropertyValue: 15px 50%
background-position-x
getPropertyValue: 15px
background-position-y
getPropertyValue: 50%
background-position: 10px 20px;
background-position
getPropertyValue: 10px 20px
background-position-x
getPropertyValue: 10px
background-position-y
getPropertyValue: 20px
No background-position set
background-position
getPropertyValue: 0% 0%
background-position-x
getPropertyValue: 0%
background-position-y
getPropertyValue: 0%