The following box should break the sequence of symbols at the 5 character mark and not overflow the blue box. This is because U+1D49E has a general category(gC) of Letter, for which break-all applies.

The following box should break between a pair of regional indicators ( U+1F1EF and U+1F1F5 ) because they (as a pair) act like Ideographs (LB=ID) whether or not 'word-break' is break-all.