The Eszett character (ß) should be rendered as "SS" when it is capitalized.
IE8 Mode, IE9 Mode, IE10 Mode, and IE11 Mode (All Versions)
The Eszett character (ß) is not rendered as "SS".
The test case fails because the Eszett character (ß) is not rendered as SS after text-transform: capitalize is applied.
This is discussed in section 2.1.80 "Section 16.5, Capitalization: the 'text-transform' property".