front: add useSimulationResults hook tests

[Maymanaf]

closes #16668
Critical behaviors covered:

• no resolved train -> returns undefined results
• complete data -> returns a valid simulation result
• partial or incomplete data -> returns an invalid result
• paced occurrences -> rebuilds the selected train correctly
• loading -> returns loading=true when any dependency is fetching

[kmer2016]

Nice work on the test coverage! I had a thought about the mock setup.

I think we should only mock the 5 actual I/O dependencies (React, Redux, RTK endpoints). The other 9 are pure functions, so mocking them adds a lot of setup without giving us much assertions end up checking that mocks were called rather than what the hook actually produces.

Also, the useMemo that builds the effective train (useSimulationResults.ts:42-72) is pure domain logic. We could extract it as a buildEffectiveTrain(selectedTrainId, timetableItem) function. Tthat way we can unit-test the occurrence/exception resolution with zero mocks.

Together with the mock cleanup above, this would simplify the hook tests a lot. Happy to handle it in a follow-up PR.

[Yohh]

thanks!

this test is set in front/src/applications/operationalStudies/__tests__/, could you set it closer in front/src/applications/operationalStudies/hooks/__tests__/?

need more time to review deeper

[Math-R]

lgtm