Also known as UAT, these are tests carried out from the view of the user are. In addition, to this, finals tests are carried out in order to determine subset of existing test cases the software being tested (the test of object) in order to count as having been successfully tested in one test level.
In terms of Zeta Test, users have the following opportunities to include external users in their testing process:
Unit testing is a software design and development method where the programmer makes sure that individual units of source code are fit for use. A unit is the smallest testable part of an application.
See also Unit testing on Wikipedia.
A use case describes a sequence of transactions resulting from the interaction between a system a person ("actor"). The expectation is that the actor receives a recognisable result after their interaction with the system.
This approach to testing is a black box test design in which the test cases are created to carry out specific use-case scenarios.