Support @ExtendWith on fields

[slu-it]

Overview

Is it planned for JUnit 5 to discover composed @ExtendWith annotations on fields?

As far as I can see (from Milestone 1) they are only discovered in case they are used on types or methods.

For projects like Mockito it would be useful to also discover extension by analyzing field annotations.

Example:

// The following explicit declaration would become unnecessary.
// @ExtendWith(MockitoExtension.class)
public class MyServiceTest {

    @Mock
    FooService fooService;

    @InjectMocks
    MyService cut;

    @Test
    void testSomething() {
        ....
    }

}

In case @Mock and @InjectMocks were to be changed to composed annotations declaring @ExtendWith(MockitoExtension.class), they could simply be used without having to declare the extension for each test class.

Related Issues

• Support programmatic extension registration via fields #497
• Introduce mechanism for programmatic extension management #506
• Support declarative extension registration on fields and parameters #864

Deliverables

• Support registration of extensions on fields with the desired extension classes supplied via @ExtendWith(...).
  • This is analogous to the current support for declaring @ExtendWith on classes and methods.

[sbrannen]

Discovery of extensions on fields is something we have in fact considered, but the feature is not currently planned. So I'll put it in the backlog now.

Thanks for raising the issue.

[sbrannen]

Overhauled this issue's description by introducing Status Quo, Proposal, and Deliverables sections with a new focus on programmatic extension registration via fields.

[sbrannen]

Currently slated for M3.