Add/1034

[PGijsbers]

Turn on lazy loading by default for datasets.
Leaving tasks for a separate PR as I notice the diff is getting big since I made some additional changes to the tests.
So only progress for #1034.

I couldn't clean up everything, but I tried to clean things up a little bit.
The use of parametrize required me to work outside of the unittest class.
I tried to still make behavior similar as possible so its easier that they're not doing wildly different things (I do think that a lot of the setup/teardown that come with the general behavior isn't really needed though).

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.28%. Comparing base (1d707e6) to head (44dcb03).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1352      +/-   ##
===========================================
- Coverage    84.33%   84.28%   -0.06%     
===========================================
  Files           38       38              
  Lines         5293     5288       -5     
===========================================
- Hits          4464     4457       -7     
- Misses         829      831       +2     

Flag	Coverage Δ
	84.28% <100.00%> (?)

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[LennartPurucker]

LGTM; very nice refactor of the tests!

Otherwise, no further comments from my side.