API Evolution
One of the major goals of JUnit 5 is to improve maintainers' capabilities to evolve JUnit despite its being used in many projects. With JUnit 4 a lot of stuff that was originally added as an internal construct only got used by external extension writers and tool builders. That made changing JUnit 4 especially difficult and sometimes impossible.
That’s why JUnit 5 introduces a defined lifecycle for all publicly available interfaces, classes, and methods.
API Version and Status
Every published artifact has a version number <major>.<minor>.<patch>, and all publicly
available interfaces, classes, and methods are annotated with @API from the
@API Guardian project. The annotation’s status attribute can be assigned one of the
following values.
| Status | Description |
|---|---|
|
Must not be used by any code other than JUnit itself. Might be removed without prior notice. |
|
Should no longer be used; might disappear in the next minor release. |
|
Intended for new, experimental features where we are looking for feedback. |