Package check is designed for testing, including table drive tests, to check the value of a returned error. The return value of a check is either an empty string (they matched) or a string describing why the check failed. Errors can be checked against different types of values (see Error) depending on the use case. Example Usage: When a string is passed, check.Error normally just checks to see that error message contains the string, case sensitive. Strings cast to Case are checked case insensitive while Equal and CaseEqual require the entire error message to be matched either case sensitive or insensitive respectively.