`TestFactory` Annotation

JUnit 5 provides the @Test annotation in the Jupiter module to write standard unit tests. These test cases assume the behavior of the test. It’s not possible to change the behavior of the tests if anything happens at runtime.

Assumptions provide a basic form of dynamic behavior but are rather limited in their expressiveness.

Jupiter introduced a new dynamic model that generates tests at runtime. These tests are called dynamic tests. They are generated at runtime by a factory method annotated with the @TestFactory annotation.

Note: The factory method with the @TestFactory annotation is not a regular test. It’s a general factory method that generates the test case.

A dynamic test is composed of a display name and an executable.

An executable is a @FunctionalInterface introduced in Java 8. This means that the implementations are provided either as a lambda expression or as a method reference.

Rules for writing @TestFactory methods

A method that is annotated with the @TestFactory annotation must return one of the following:

• A single DynamicNode object
• A stream of DynamicNode objects
• A collection of DynamicNode objects
• An iterable of DynamicNode objects
• An iterator of DynamicNode objects
• An array of DynamicNode objects

Similar to tests annotated with @Test annotation, factory methods annotated with @TestFactory must not be private or static. They are allowed to have the access modifier as package-private.

Code example