Why:
* The inclusion matcher (when used with the `in_array` qualifier) makes
the assertion that when the attribute is set to a value that is
outside the given array, the record in question is invalid. The issue
is that when used with a date or datetime attribute, the arbitrary
value the matcher chose was a string. This was getting typecast and so
the matcher was throwing a CouldNotSetAttributeError.
To satisfy the above:
* If the column is a date, use a Date for the arbitrary value
* If the column is a datetime, use a DateTime for the arbitrary value
* If the column is a time, use a Time for the arbitrary value
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