Make it easier to test code for different inputs

[Zomis]

Possibly something like this:

$ input 'ABCDEF' produces 'FEDCBA'
$ input 'qwerty' produces 'QWERTY'
$ input 'abc' validator 'groovyScript'

When running this code in some mode, the code is then tested with all those different inputs to make sure it produces the expected results.

[Zomis]

Related to #23 but that issue does not take user inputs into consideration