Hi Till, immediate benefit would be mostly nested tests for a better test structure and new parameterized tests for less clutter (often test functionality is split into parameterized test and non-parameterized test because of JUnit4 limitation). Additionally, having Java8 lambdas to perform fine-grain exception handling would make all related tests more readable (@Test only allows one exception per test method, while in reality we often have more exceptions / more fine grain assertions and need to resort to try-catch -- yuck!). The extension mechanism would also make the mini cluster much easier to use: we often have to start the cluster manually because of test-specific configuration, which can be easily avoided in JUnit5.
In the medium and long-term, I'd also like to use the modular infrastructure and improved parallelization. The former would allow us better to implement cross-cutting features like TestLogger (why do we need to extend that manually in every test?). The latter is more relevant for the next push on CI, which would be especially interesting with e2e being available in Java. On Mon, Nov 30, 2020 at 2:07 PM Dawid Wysakowicz <dwysakow...@apache.org> wrote: > Hi all, > > Just wanted to express my support for the idea. I did miss certain > features of JUnit 5 already, an important one being much better support > for parameterized tests. > > Best, > > Dawid > > On 30/11/2020 13:50, Arvid Heise wrote: > > Hi Chesnay, > > > > The vintage runner supports the old annotations, so we don't have to > change > > them in the first step. > > > > The only thing that we need to change are all rules that do not extend > > ExternalResource (e.g., TestWatcher used in TestLogger). This change > needs > > to be done swiftly as this affects the shared infrastructure as you have > > mentioned. > > > > Only afterwards, we start to actually migrate the individual tests. That > > can be done module by module or as we go. I actually found a nice article > > that leverages the migration assist of IntelliJ [1]. > > > > As the last stop, we remove the vintage runner - all JUnit4 tests have > been > > migrated and new tests cannot use old annotation etc. anymore. > > > > [1] > > > https://blog.jetbrains.com/idea/2020/08/migrating-from-junit-4-to-junit-5/ > > > > On Mon, Nov 30, 2020 at 1:32 PM Chesnay Schepler <ches...@apache.org> > wrote: > > > >> I presume we cannot do the migration module-wise due to shared test > >> utilities that rely on JUnit interfaces? > >> > >> On 11/30/2020 1:30 PM, Chesnay Schepler wrote: > >>> Is it feasible that 2 people can do the migration within a short > >>> time-frame (say, a week)? > >>> Must the migration of a test be done in one go, or can we for example > >>> first rename all the Before/After annotations and then to the rest? > >>> Are there any issues with other test dependencies (i.e., hamcrest, > >>> powermock (PowerMockRunner), mockito) that we should be aware of? > >>> > >>> I generally like the idea of using JUnit 5, but am wary of this > >>> migration dragging on for too long. > >>> > >>> On 11/27/2020 3:29 PM, Arvid Heise wrote: > >>>> Dear devs, > >>>> > >>>> I'd like to start a discussion to migrate to a higher JUnit version. > >>>> > >>>> The main motivations are: > >>>> - Making full use of Java 8 Lambdas for writing easier to read tests > >>>> and a > >>>> better performing way of composing failure messages. > >>>> - Improved test structures with nested and dynamic tests. > >>>> - Much better support for parameterized tests to avoid separating > >>>> parameterized and non-parameterized parts into different test classes. > >>>> - Composable dependencies and better hooks for advanced use cases > >>>> (TestLogger). > >>>> - Better exception verification > >>>> - More current infrastructure > >>>> - Better parallelizable > >>>> > >>>> Why now? > >>>> - JUnit5 is now mature enough to consider it for such a complex > project > >>>> - We are porting more and more e2e tests to JUnit and it would be a > >>>> pity to > >>>> do all the work twice (okay some already has been done and would > >>>> result in > >>>> adjustments, but the sooner we migrate, the less needs to be touched > >>>> twice) > >>>> > >>>> Why JUnit5? > >>>> There are other interesting alternatives, such as TestNG. I'm happy > >>>> to hear > >>>> specific alternatives. For now, I'd like to focus on JUnit4 for an > >>>> easier > >>>> migration path. > >>>> > >>>> Please discuss if you would also be interested in moving onward. To > get > >>>> some overview, I'd like to see some informal +1 for the options: > >>>> > >>>> [ ] Stick to JUnit4 for the time being > >>>> [ ] Move to JUnit5 (see migration path below) > >>>> [ ] Alternative idea + advantages over JUnit5 + some very rough > >>>> migration > >>>> path > >>>> > >>>> --- > >>>> > >>>> Migrating from JUnit4 to JUnit5 can be done in some steps, so that we > >>>> can > >>>> gradually move from JUnit4 to JUnit5. > >>>> > >>>> 0. (There is a way to use JUnit4 + 5 at the same time in a project - > >>>> you'd > >>>> use a specific JUnit4 runner to execute JUnit5. I'd like to skip this > >>>> step > >>>> as it would slow down migration significantly) > >>>> 1. Use JUnit5 with vintage runner. JUnit4 tests run mostly out of the > >>>> box. > >>>> The most important difference is that only 3 base rules are supported > >>>> and > >>>> the remainder needs to be migrated. Luckily, most of our rules derive > >>>> from > >>>> the supported ExternalResource. So in this step, we would need to > >>>> migrate > >>>> the rules. > >>>> 2. Implement new tests in JUnit5. > >>>> 3. Soft-migrate old tests in JUnit5. This is mostly a renaming of > >>>> annotation (@Before -> @BeforeEach, etc.). Adjust parameterized tests > >>>> (~400), replace rule usages (~670) with extensions, exception handling > >>>> (~1600 tests), and timeouts (~200). This can be done on a test class > by > >>>> test class base and there is no hurry. > >>>> 4. Remove vintage runner, once most tests are migrated by doing a > final > >>>> push for lesser used modules. > >>>> > >>>> Let me know what you think and I'm happy to answer all questions. > >>>> > >>> > >> > > -- Arvid Heise | Senior Java Developer <https://www.ververica.com/> Follow us @VervericaData -- Join Flink Forward <https://flink-forward.org/> - The Apache Flink Conference Stream Processing | Event Driven | Real Time -- Ververica GmbH | Invalidenstrasse 115, 10115 Berlin, Germany -- Ververica GmbH Registered at Amtsgericht Charlottenburg: HRB 158244 B Managing Directors: Timothy Alexander Steinert, Yip Park Tung Jason, Ji (Toni) Cheng
