#data
<div xmlns="http://www.w3.org/1999/xhtml" is="ab-cd">x</div>
#errors

#data
<hoge xmlns="http://www.w3.org/1999/xhtml" is="ab-cd">x</hoge>
#errors
/hoge;element not defined;m

#data
<hoge xmlns="http://www.w3.org/2000/svg" is="ab-cd">x</hoge>
#errors
/hoge;unknown namespace element;u
/hoge/@is;unknown attribute;u

#data
<hoge xmlns="http://test/" is="ab-cd">x</hoge>
#errors
/hoge;unknown namespace element;u
/hoge/@is;unknown attribute;u

#data
<div xmlns="http://www.w3.org/1999/xhtml" is="">x</div>
#errors
/div/@is;is:not custom element name;m

#data
<div xmlns="http://www.w3.org/1999/xhtml" is="-cd">x</div>
#errors
/div/@is;is:not custom element name;m

#data
<embed xmlns="http://www.w3.org/1999/xhtml" is="-cd" src="x"></embed>
#errors
/embed/@is;is:not custom element name;m