Validate: 'Validate'
In 0liver0815/onc-crmpack-test: Object-Oriented Implementation of CRM Designs

The Validate class is a Reference Class to help programming validation for new S4 classes.

Starting from an empty msg vector, with each check that is returning FALSE the vector gets a new element - the string explaining the failure of the validation.

msg: (character)
the cumulative messages.

check(test, string = ""): Check whether the test is TRUE; if so, return NULL. Otherwise, add the string message into the cumulative messages vector msg.
result(): Return either cumulative messages vector msg (which contains the error messages from all the checks), or NULL, if msg is empty (i.e. all the checks were successful).