NPE when using nested JUnit5 classes

[acoburn]

When using the quarkus-junit5 module (Quarkus version 0.23.2) with the @QuarkusTest annotation, any @Nested JUnit5 classes consistently lead to null pointer exceptions.

The relevant portion of the stack trace is:

org.junit.jupiter.api.extension.TestInstantiationException: TestInstanceFactory [io.quarkus.test.junit.QuarkusTestExtension] failed to instantiate test class [org.acme.quickstart.GreetingResourceTest$NestedClass]: Bean is null
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstanceFactory(ClassBasedTestDescriptor.java:300)
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateTestClass(ClassBasedTestDescriptor.java:275)
	[ ... ]
Caused by: java.lang.NullPointerException: Bean is null
	at java.base/java.util.Objects.requireNonNull(Objects.java:246)
	at io.quarkus.arc.BeanManagerImpl.getReference(BeanManagerImpl.java:54)
	at io.quarkus.test.common.TestInstantiator.instantiateTest(TestInstantiator.java:25)
	at io.quarkus.test.junit.QuarkusTestExtension.createTestInstance(QuarkusTestExtension.java:368)
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstanceFactory(ClassBasedTestDescriptor.java:285)
	... 82 more

I can reproduce this consistently in JDK8 and JDK11, with both Gradle and Maven build environments.

A minimal example of this error can be found at https://github.com/acoburn/quarkus-junit5-test, which is built from the getting-started archetype. The only change to the generated code is that the JUnit @Test is wrapped in a @Nested class.

[geoand]

So after debugging a bit I saw that Arc doesn't support non-static inner classes (see this).
So I'm not sure how @Nested can be supported. @manovotn @mkouba WDYT?

[manovotn]

@geoand In Junit testing with Quarkus, the test class itself is a bean (see this code).
And CDI spec doesn't like inner classes (non static), see https://docs.jboss.org/cdi/spec/2.0/cdi-spec.html#what_classes_are_beans

[manovotn]

Although I agree that we should remedy the error and make it more readable.
We could probably detect this in QuarkusTestExtension#createTestInstance() and throw and exception?

[geoand]

@geoand In Junit testing with Quarkus, the test class itself is a bean (see this code).

Yup, that's why I looked at Arc in the first place :)

We could probably detect this in QuarkusTestExtension#createTestInstance() and throw and exception?

Sounds reasonable to me

[manovotn]

Ok, in that case, I'll send a PR for that later today.

[geoand]

Cool, thanks!

[manovotn]

@acoburn BTW if you really need it to be @Nested for some reason, then you can make it static and that will work too.

[geoand]

I think that @Nested in JUnit 5 is not supposed to be static.

But of course the question of the usefulness of @Nested is still valid. I personally haven't encountered it.

[manovotn]

Ah, you're right, just spotted that in their docs - https://junit.org/junit5/docs/current/user-guide/#writing-tests-nested

But of course the question of the usefulness of @nested is still valid. I personally haven't encountered it.

Yeah, I've got similar experience.

[acoburn]

@manovotn thanks for fixing this so quickly. While it would be nice to use @Nested classes at some future point, I can work around that. The NPE issue described here has been fixed, so I am going to close this issue.