This is a testharness.js-based test.
PASS Registering valid custom element name starting with '_' char 
FAIL Registering valid custom element name starting with base char assert_unreached: The custom element name '℮-x212e' should be registered without errors Reached unreachable code
PASS Registering valid custom element name starting with ideographic char 
PASS Registering custom element starting with invalid character (general) should fail 
PASS Registering custom element starting with invalid character (combining char) should fail 
PASS Registering custom element starting with invalid character (extender char) should fail 
PASS Registering custom element starting with invalid character (digit char) should fail 
Harness: the test ran to completion.

