How can I use @ParameterizedClass and @Isolated together?

[vlsi]

I have a test that uses @ParameterizedClass: https://github.com/pgjdbc/pgjdbc/blob/f61437db78c2196df005ff60d8df23b617e4d95c/pgjdbc/src/test/java/org/postgresql/test/jdbc2/ResultSetTest.java#L54

One of the tests uses Locale.setDefault, so I want to make sure JUnit does not execute the class/test concurrently with the others.

I want to keep concurrent test execution.

How can I achieve the goal with JUnit 5? (I need the tests to be runnable with Java 8)

[marcphilipp]

One of the tests uses Locale.setDefault, so I want to make sure JUnit does not execute the class/test concurrently with the others.

@Isolated is only applicable to test classes, not methods. Putting it on @ClassTemplate class currently fails and I've just opened an issue to fix that:

• Class templates should be able to declare @ResourceLock #5155

Instead of @Isolated, you could annotate all methods that read/write Locale.getDefault() with a @ResourceLock annotation (or use Pioneer's @ReadsDefaultLocale and @WritesDefaultLocale). However, there are currently somee issues with that as well:

• Make @ResourceLock applicable to class templates (its invocations, that is) #5025
• Applying @ResourceLock to a single method in a class template completely turns off parallel execution for this class template #5033

Until those issues are resolved, I think your best bet is to move the test method using Locale.setDefault to a separate class unparameterized class and annotate it with @Isolated.

[vlsi]

I am not sure @ReadsDefaultLocale is viable for my case, as I can't predict which tests do read default locale.
Any of them might read the default locale, so I would prefer @Isolated for isolating the tests that do modify the locale.