Editing Unit testing (section)

== Unit ==
A unit is defined as a single behaviour exhibited by the system under test (SUT), usually corresponding to a requirement{{Definition needed|date=January 2025}}. While a unit may correspond to a single function or module (in [[procedural programming]]) or a single method or class (in [[object-oriented programming]]), functions/methods and modules/classes do not necessarily correspond to units. From the system requirements perspective only the perimeter of the system is relevant, thus only entry points to externally visible system behaviours define units.{{Clarify|date=January 2025}}<ref>{{cite book |last=Beck
|first=Kent
|author-link=Kent Beck
|date=2002
|title= Test-Driven Development by Example 
|publisher=Addison-Wesley
|isbn=978-0321146533}}</ref>