Test FakeListener for fill-dummy-data option

[YooSunYoung]

Now we are updating the beamlime to use nexus file to use static information including FakeListener starting with #242 .

Existing tests already cover a lot of the updated parts but we still need to add tests for fill-dummy-data option if it is actually retrieving data from the file if asked.

The ymir_detectors.nxs file does not have any event data, so we may want to make a temporary file and add event data, and then see if the result is as expected.

[SimonHeybrock]

It obviously works correctly, may not be worth adding a test that may require frequent refactoring.

[YooSunYoung]

Hmm yeah ... Maybe it's not so important since we already used it for manual testing a lot...