Re: [Junit-devel] ClassRules

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

Alistair,

[I need to try to remember "reply all" and CC junit-devel so that
everyone stays involved; I keep forgetting]

On Sat, Oct 24, 2009 at 10:02 PM, Alistair Israel <ai...@gm...> wrote:
> On Fri, Oct 23, 2009 at 9:25 PM, David Saff <da...@sa...> wrote:
>
>> 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?
>
> Hi, again, David.
>
> Finally remembered another reason (in fact, my primary reason) for
> reusing @Rule.
>
> While in some cases, separating a ClassRule from a MethodRule makes
> sense (and allows for mixing and matching), in other cases that simply
> breaks encapsulation.
>
> The basic case is an expensive factory object or setup code that's
> used to provide a new instance of a resource to each @Test method. The
> ClassRule performs "around Class" setup & teardown, but the MethodRule
> would use the first to get new instance of the resource (which it uses
> for "around @Test" behavior).
>
> Consider a remote Web service that's used to report test results and
> timings to. (I know, it sounds contrived, but I don't want to keep
> harping about my own embedded DB + JPA + dependency injection use
> case.)
>
> The setup of the Web service is expensive, and ideally we'd want to
> set it up once before all tests, and cleanup after everything's done.
> Meanwhile, around each test we want to report start then
> success/failure.
>
> We could separate the two using:
>
>    @ClassRule
>    public static TestReportingWebService service = new
> TestReportingWebService();
>
>    @Rule
>    public RemoteTestWatchman watchman = new RemoteTestWatchman(service);
>
> Or, in my mind it'd be nicer to be able to go:
>
>    @Rule
>    public static RemoteTestWatchman watchman = new RemoteTestWatchman();

Note that we can get the "one object" behavior with the "two annotations" API:

@ClassRule
public static RemoteTestWatchman watchman = new RemoteTestWatchman();

@Rule public RemoteTestWatchman methodWatchman = watchman;

Is this better?

   David