Testable

A piece of code is testable when it may have related tests, that checks its behavior.

To make a code testable, the following features are useful:

• Dependency injection

• Programming to interface

• Single responsability principle

• No global state

• No static methods

• No New in business logic

• Pure functions

• Deterministic functions

• No direct output

• No usage of exit()

The golden rule: If it is not possible to write a test for it without setting up the whole world first, the code is not testable.

Documentation

See also Improve your PHP code testability and Manual:Writing testable PHP code.

Related : Exit, Deterministic, Single Responsability Principle (SRP), Static Method, Static Property, Business Logic, Pure Function, Direct Output, Dependency Injection, Program To Interface, Maintenability