Resources extension: Consider running tests sequentially when lifecycle methods have resources

When tests and lifecycle methods share the same @Shared resource, they are forced to run sequentially, even if parallel tests have been enabled. This prevents methods from mutating the resource at the same time.

However, it is a common pattern in JUnit to save some data in a field from inside a lifecycle method. This is error-prone because if a resource is saved in a field by a @BeforeAll method, then the @Tests will run in parallel as they are not annotated with @Shared directly, and thus they are free to mutate the resource at the same time.

To prevent this, we should consider running all tests in a test class sequentially (including all @Nested classes) when the class has a lifecycle method with a @Shared parameter.

[jbduncan]

I like it! It makes it clear what the user should be doing instead.

[nipafx]

I think that’s ok. I’m editing the docs as we ~speak~ write - should I add this sentence?

Instead, use @Shared to reuse resources in multiple tests.