test(junit): rename misleading 'unexpected' tests

[aviavi16]

The tests named "should render unexpected" exercise expect() assertion failures (JUnit ),
not unexpected runtime errors ().

Renaming improves clarity and avoids confusion when working on JUnit error vs failure reporting.

[aviavi16]

Why rename the tests?
This prevents confusion in the context of discussions around JUnit vs (see #12944).
The name “unexpected” suggests a runtime error (), while these tests actually exercise expect() assertion failures ().

Because of that mismatch, it can look like the tests are related to or even “cover” #12944, while in practice they do not.
Renaming makes the intent explicit and avoids misleading conclusions when working on JUnit error/failure reporting.

Regarding the “after retry” test:
That test was renamed as well, so both the base case and the retry scenario are consistently covered.