Refactor textfile parsing to be unit testable

[KatieProchilo]

Separation of concerns: Logic to verify path are valid and logic for split string in .txt file should exist as stand alone not tightly coupled.

1. parseTextFile should be split into 2 separate units, retrieveDataFromFile & splitDataIntoTestUnits, code coverage will focus on testing splitDataIntoTestUnits.

[Joll59]

Next PR will follow advised naming convention above.
With addition of validation functions.
New method names:
validateFile
validateFolder
retrieveFileContent ===> retrieveDataFromFile
parseTextFileContent===>splitDataIntoTestUnits
createTestData ... should this be called createTestUnits ??