Investigate JUnit 5

JUnit 5 looks like it might be a very awkward upgrade for both our users and Spring Boot itself. We’ll need to come up with a plan going forward for how people should upgrade.

Of particular concern:

• You can’t just run JUnit 4 tests with JUnit 5 😢
• There are new @Test annotations and expectedException has been dropped
• There is no @Rule annotation (this will break a lot of our tests and we’ll need to offer alternatives to the rules we offer)

We might be able to offer JUnit 5 alongside JUnit 4 for a while (possibly a long while) so that people can use both.

I imagine probably going to frustrate a lot of users given that mostly their own test code has very little direct contact with the JUnit API. Mostly people use @Test, @Before/@After, perhaps a few @Rule annotations and some Assert calls.

Related issue https://github.com/junit-team/junit5/issues/169

[philwebb]

Spring Boot 2.2 will switch to JUnit 5 by default. This issue has now been superseded by the following issues:

• #13739
• #14736
• #14738
• #16942
• #16957
• #16959
• #17029

[philwebb]

@sdeleuze Oh wow. That was a total typo. I meant to say we should not switch 😕