I don't have time to do a review, so I'll just write here.
There are two problems :

• Your test is too complicated to test something too simple, you need to simplify it, create methods or classes for this so your test can be as simple as for example assertEquals(sendEval("2+2"), new JShellResult(...))
• Also include a test to test state. For example, you can send an eval "var list = List.of(1, 2, 3)" and then send a separate eval like "println(list)"

Hello @Alathreon !

Your test is too complicated to test something too simple

I think that my test code is pretty simple, it uses WebTestClient API to establish test in a smooth way (ig it's a good practice as mentioned in spring docs) :

create methods or classes for this so your test can be as simple as for example assertEquals(sendEval("2+2"), new JShellResult(...))

I'm not certain i understand this sorry, can u elaborate ?