Create tests for brainmapper sub-module

[K-Meech]

More tests need to be added for the brainmapper sub-module - aiming at >90% coverage.

[K-Meech]

I'm looking into writing tests for the summarise_points_by_atlas_region function. This requires a corresponding BrainGlobeAtlas object, but I'm not sure which one corresponds to the test volume.csv file.

Any ideas? @alessandrofelder

[alessandrofelder]

My guess is that's it's an Allen one (I know it's definitely a mouse thanks to @niksirbi ) - I would try using BrainGlobeAtlas("allen_mouse_100um") in the tests (because it's the lowest res one) and see how far you get?

@adamltyson may know more exactly how this data was generated?

[adamltyson]

I assume it's allen_mouse_something. No idea which, but to some level of precision, it shouldn't matter. The volumes are in mm^3 and that's the same across all resolutions.