PASS "foo\0" becomes "foo�"
PASS "f\0oo" becomes "f�oo"
PASS "\0foo" becomes "�foo"
PASS "\0" becomes "�"
PASS "\0\0\0" becomes "���"
PASS "fooU+d800" becomes "foo�"
PASS "fU+d800oo" becomes "f�oo"
PASS "U+d800foo" becomes "�foo"
PASS "U+d800" becomes "�"
PASS "U+d800U+d800U+d800" becomes "���"