It would be really great if there were java tooling to actually compile
separate production binaries and test binaries based on annotations like this,
rather than having to ship methods that were only exposed for testing.
If such a preprocessor does exist, @TestOnly provides a stronger, unambiguous
contract: any method with than annotation can be dropped for the production
build. However, @VisibleForTesting is weak, because it does not express what
the correct lower visibility ought to be, so automation would be impossible.
If we decide to allow both, I agree that both annotations should never appear
on the same entity, since the contracts are incompatible: @TestOnly must be
used by tests only, while @VisibleForTesting by definition is also used in
production.
It seems that @VisibleForTesting is a "lazy" shortcut -- instead of adding that
annotation, you could instead create a delegating method annotated with
@TestOnly, at the cost of 4 "extra" lines of code.
On 11/4/21, 3:30 PM, "Eric Zoerner" <zoern...@vmware.com> wrote:
My opinion is that @VisibleForTesting is a code smell and either indicates
that there is refactoring needed or there are tests that are unnecessary. If
there is functionality in a private method that needs to be tested
independently, then that code should be extracted and placed in a separate
class that has a wider visibility that can be tested on its own.
The same could probably be said for @TestOnly unless there are actually
static analysis tools that need it for some reason.
From: Kirk Lund <kl...@apache.org>
Date: Thursday, November 4, 2021 at 15:13
To: dev@geode.apache.org <dev@geode.apache.org>
Subject: Re: @TestOnly or @VisibleForTesting
As everyone thinks about how we want to use these annotations, please keep
this in mind that both *@VisibleForTesting* and *@TestOnly* can be used on
Types (Class/Interface/Enum), Constructors, Methods and Fields. (not just
Methods)
On Thu, Nov 4, 2021 at 3:09 PM Kirk Lund <kl...@apache.org> wrote:
> Hey all,
>
> We're introducing a mess to the codebase. It's a small problem, but
> several small problems become a big problem and one of my missions is to
> clean up and improve the codebase.
>
> I recently started seeing lots of pull requests with usage of @TestOnly.
> Sometimes it's used instead of @VisibleForTesting, while sometimes I see
> both annotations added to the same method.
>
> Before we start using @TestOnly, I think we need some guidelines for when
> to use @TestOnly versus @VisibleForTesting. Or if we're going to replace
> @VisibleForTesting with @TestOnly, then we either need a PR for the
> replacement or, at a minimum, deprecation annotation and javadocs added to
> VisibleForTesting.java.
>
> The annotations appear similar but the javadocs describe slightly
> different meanings for them...
>
> *@VisibleForTesting* was created in Geode several years ago to mean that
> the method is either only for testing or the visibility of it was widened
> (example: a private method might be widened to be package-private,
> protected or public). The method might be used by product code, but it
also
> has widened scope specifically to allow tests to call it. The javadocs
say:
>
> "Annotates a program element that exists, or is more widely visible than
> otherwise necessary, only for use in test code.
>
> Introduced while mobbing with Michael Feathers. Name and javadoc borrowed
> from Guava and AssertJ (both are Apache License 2.0)."
>
> *@TestOnly* started appearing when we added org.jetbrains.annotations
> dependency earlier this year. It seems to indicate a method that is ONLY
> used for tests (never called by product). The javadocs say:
>
> "A member or type annotated with TestOnly claims that it should be used
> from testing code only.
>
> Apart from documentation purposes this annotation is intended to be used
> by static analysis tools to validate against element contract violations.
>
> This annotation means that the annotated element exposes internal data and
> breaks encapsulation of the containing class; the annotation won't prevent
> its use from production code, developers even won't see warnings if their
> IDE doesn't support the annotation. It's better to provide proper API
which
> can be used in production as well as in tests."
>
> So... when do we use one over the other? I don't think both annotations
> should be on the same method. Also, some sort of guidelines are needed if
> we're going to start using @TestOnly.
>
