+1 BR, Xiangying
On Tue, Aug 26, 2025 at 10:13 AM Ruimin MA <maruimin...@gmail.com> wrote: > > thanks for sharing this. It's really helpful and good to know that! > > > Yunze Xu <x...@apache.org>于2025年8月25日 周一21:39写道： > > > Hi all, > > > > I'd like to bring the open discussion for the coding style about > > whether to use reflection in tests. Today when I reviewed a PR, I left > > a comment here [1] because I noticed reflection was used again in > > tests. > > > > Reflection makes refactoring really painful and could kill the > > enthusiasm to refactor the existing bad quality code. [2] is an > > example when I tried to replace ConcurrentOpenHashMap with > > ConcurrentHashMap. You can find how many `WhiteboxImpl` references are > > in that PR. The painful point is that if a field's type is changed and > > this field was accessed via reflection in tests, it could not be > > detected during compilation. > > > > I can feel the pain because I've contributed many refactoring PRs to > > improve the code, it really has annoyed me many times when I found a > > new failed test due to not being exposed by reflection. > > > > Even regardless of the refactoring, using reflection in tests is a bad > > practice. Pulsar has adopted Java 17 for years, though many people > > still don't like `var`. You can compare the following two sentences: > > > > ```java > > ConcurrentOpenHashMap<String, PersistentSubscription> subscriptions = > > WhiteboxImpl.getInternalState(persistentTopic, "subscriptions"); > > ``` > > > > ``` > > var subscriptions = persistentTopic.getSubscriptions(); > > ``` > > > > The 1st one is really long and hard to refactor, while the 2nd one is > > short and scalable so that it works even if `getSubscriptions` returns > > a different map type in future. I know the debate about anonymous > > typing widely exists. But anyway, nearly all modern languages have > > adopted this solution, e.g. `var`, `let`, `auto`, `val`. I don't mean > > to say using `var` is always better than writing the full type name. > > But anyway, you can write the type name if you want, like: > > > > ``` > > Map<String, Subscription> subscriptions = > > persistentTopic.getSubscriptions(); > > ``` > > > > It's still more short and scalable than the 1st one. > > > > The only disadvantage of exposing a field's visibility for tests is > > that it breaks the encapsulation. But we really don't need much > > encapsulation for non-public APIs. And we have the > > `@VisibleForTesting` annotation. Getters and setters in Java have been > > criticized by many users of other languages. Keeping a field private > > and using reflection to access it really looks like a joke. > > > > Therefore, I hope when you're reviewing PRs, please prevent > > reflections in tests as much as possible. > > > > [1] https://github.com/apache/pulsar/pull/24658#discussion_r2298080559 > > [2] https://github.com/apache/pulsar/pull/23320/files > > [3] > > https://stackoverflow.com/questions/2811141/is-it-bad-practice-to-use-reflection-in-unit-testing > > > > Thanks, > > Yunze > >
