assert_not UTF8.valid?("\xC2\xC2") # 2-byte multibyte identifier, followed by another one
assert_not UTF8.valid?("\x4a\x82") # plain ASCII, followed by multibyte continuation
assert_not UTF8.valid?("\x82\x82") # multibyte continuations without multibyte identifier
assert_not UTF8.valid?("\xC2\xC2") # 2-byte multibyte identifier, followed by another one
assert_not UTF8.valid?("\x4a\x82") # plain ASCII, followed by multibyte continuation
assert_not UTF8.valid?("\x82\x82") # multibyte continuations without multibyte identifier