Test case can be even simple as you do not use the foreign characters to reproduce the problem. You can just use:
insert into t1 values (1, 'abc')
and it will be the same error. It is not what you inserted that causes the error, but that the row has been widened on the same. The unsupported chars will be converted as "?" anyway, for example:
insert into t1 values (2, _utf8mb4 x'F09D8C86')
will be converted as "2,?" in the master table and will be replicated as such on slave.
Test case can be even simple as you do not use the foreign characters to reproduce the problem. You can just use:
insert into t1 values (1, 'abc')
and it will be the same error. It is not what you inserted that causes the error, but that the row has been widened on the same. The unsupported chars will be converted as "?" anyway, for example:
insert into t1 values (2, _utf8mb4 x'F09D8C86')
will be converted as "2,?" in the master table and will be replicated as such on slave.