What is domain testing?

Domain testing is a functional testing method that tests whether each module in the software system accepts input within the accepted domain and produces the expected output. Domain testing, with a minimal number of inputs, aims to ensure that out-of-range and invalid input values are rejected by the system and any unexpected behavior is caught. Domain testing is considered one of the most vital White Box Testing methods.

How to perform domain testing

First, the domain is partitioned into equivalence classes, which are mutually exclusive subsets of the domain. For each equivalence class, the following tests are constructed:

• Boundary-Value Analysis: Valid and invalid values at the boundary of the class are tested. Let’s take the example of input variable X with equivalence class $0-50$. The valid input values that will be tested are $0$ and $50$ to determine correct behavior at the boundary. The invalid values $-1$ and $51$ will be tested to determine that these out-of-range values are rejected correctly.
• Equivalence Partition Values: One valid input value is taken from the middle of the equivalence class that wholly represents the condition of the class. In the above example, $25$ will be a valid equivalence partition value on which the test can be performed.

The following table can be constructed for the domain testing document: