Update tests

[skim0119]

• Multi-channel signal visualization output
• Datset downloader robustness check

[codecov-commenter]

Codecov Report

Merging #78 (59599a1) into update-0.1.2 (b5fdab0) will increase coverage by 16.71%.
The diff coverage is 100.00%.

@@                Coverage Diff                @@
##           update-0.1.2      #78       +/-   ##
=================================================
+ Coverage         44.94%   61.65%   +16.71%     
=================================================
  Files                35       35               
  Lines              1137     1098       -39     
  Branches            126      123        -3     
=================================================
+ Hits                511      677      +166     
+ Misses              612      406      -206     
- Partials             14       15        +1     

Flag	Coverage Δ
unittests	61.65% <100.00%> (+16.71%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
miv/datasets/criticality.py	100.00% <ø> (+100.00%)	⬆️
miv/datasets/optogenetic.py	100.00% <ø> (+100.00%)	⬆️
miv/datasets/utils.py	98.79% <100.00%> (+98.79%)	⬆️
miv/visualization/__init__.py	100.00% <100.00%> (ø)
miv/visualization/raw_signal.py	100.00% <100.00%> (+100.00%)	⬆️
miv/__init__.py	100.00% <0.00%> (ø)
miv/mea/grid.py	57.14% <0.00%> (+57.14%)	⬆️
miv/mea/protocol.py	66.66% <0.00%> (+66.66%)	⬆️
... and 4 more

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