It is an instance of the xUnit architecture for unit testing frameworks that originated with SUnit and became popular with JUnit.

A unit test provides a strict, written contract that the piece of code must satisfy.

As a result, unit tests find problems early in the development cycle.

PHPUnit can output test results in a number of different formats, including JUnit XML and TestDox.

A vulnerability that allowed attackers to execute remote code via PHPUnit was discovered in late 2017.