MySQL 5.5 does not support casting to all targets. According to [1], these are the targets that are supported:

CAST(expr AS type)

The CAST() function takes an expression of any type and produces a result value of a specified type, similar to CONVERT(). See the description of CONVERT() for more information.

CONVERT(expr,type), CONVERT(expr USING transcoding_name)

The CONVERT() and CAST() functions take an expression of any type and produce a result value of a specified type.

The type for the result can be one of the following values:

BINARY[(N)]
CHAR[(N)]
DATE
DATETIME
DECIMAL[(M[,D])]
SIGNED [INTEGER]
TIME
UNSIGNED [INTEGER]

These failures are expected on MySQL. The tests should be skipped for MySQL.

[1] https://dev.mysql.com/doc/refman/5.5/en/cast-functions.html#function_convert