Прислали ссылку. Unit Testing in Delphi

http://forms.embarcadero.com/DelphiUnitTesting2-12

Скажу честно - я пока сам мало, что понял.

Под одним только "подпишусь":
"Without unit tests your code is fragile, hard to change, and unreliable. Unit testing is the only way that you can be sure that your code does what it is supposed to do.Without unit tests your code is fragile, hard to change, and unreliable. Unit testing is the only way that you can be sure that your code does what it is supposed to do."