Re: [Junit-devel] ClassRules

[David S. <da...@sa...>]

Alistair,

I think class-level rules make a lot of sense.  Do you think re-using
the @Rule annotation is better than a new @ClassRule annotation?

   David

On Mon, Oct 19, 2009 at 6:05 AM, Alistair Israel <ai...@gm...> wrote:
> Hi, list.
>
> Hope I'm not overstepping by just barging in like this. Anyway, I'm
> one of those early adopters of JUnit 4.7's new @Rules.
>
> As I use them more and more I've also been seeing the usefulness of
> class-level rules more and more.
>
> A concrete use case of mine is initializing a JPA (Hibernate)
> persistence context backed by an embedded Derby database, then using
> DbUnit to load fixtures and populate the database.
>
> Using JUnit 4.7, I'm able to accomplish the above using a single
> MethodRule that does everything for every test method. The performance
> drawback should be obvious—we need to initialize Derby DB, set up
> Hibernate JPA, scan for annotated classes and create the tables to
> match the entities for _every test method_.
>
> I've taken the liberty of forking, branching, and committing some
> changes to JUnit that allow for class-level rules. It's up on GitHub,
> and the meat of the changes are here:
>  http://github.com/AlistairIsrael/junit/commit/79ef5a7e1d7fa144cc81c9414f4791aaea8b3d75
>
> The gist of it:
>  * Created the ClassRule interface that declares the apply(Statement,
> TestClass) method.
>  * Modified ParentRunner to scan for fields that are a) annotated
> with @Rule, b) static, and c) implement ClassRule.
>  * If any are found, then apply them in the order found, allowing
> them to append to the head of the Statement chain.
>  * Modified BlockJUnit4ClassRunner so validation treats ClassRules
> appropriately, and only apply MethodRules in methodBlock()
>
> I've also added a ClassRulesTest to AllTests to verify the above.
>
> Using a local-build, I successfully refactored my specific use-case
> and split the compound rule into a separate ClassRule (set up Derby
> and Hibernate) and a MethodRule (load DbUnit fixtures). Not only are
> the resulting tests more efficient, this strategy lets each Rule to be
> used independently, even allows for mixing and matching of different
> database, JPA or fixtures providers.
>
> I have a few more ideas on where this can go, but I'd like to get some
> feedback first if this is something that's welcome or if you guys have
> another direction you think we should take.
>
> Thanks,
> - alistair
> --
> http://alistairisrael.wordpress.com
>
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