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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 >
