feat(tests): add more Extensions unit tests

[ghiscoding]

No description provided.

[codecov-io]

Codecov Report

Merging #184 into master will increase coverage by 6.31%.
The diff coverage is 99.42%.

@@            Coverage Diff             @@
##           master     #184      +/-   ##
==========================================
+ Coverage    41.8%   48.11%   +6.31%     
==========================================
  Files         160      160              
  Lines        7075     7062      -13     
  Branches     2243     2237       -6     
==========================================
+ Hits         2957     3397     +440     
+ Misses       4117     3664     -453     
  Partials        1        1

Impacted Files	Coverage Δ
...elia-slickgrid/extensions/columnPickerExtension.ts	100% <100%> (+77.28%)	⬆️
src/aurelia-slickgrid/services/grid.service.ts	100% <100%> (ø)	⬆️
.../aurelia-slickgrid/extensions/gridMenuExtension.ts	100% <100%> (+88.5%)	⬆️
...ia-slickgrid/extensions/rowMoveManagerExtension.ts	100% <100%> (+75%)	⬆️
...slickgrid/extensions/draggableGroupingExtension.ts	100% <100%> (+67.86%)	⬆️
...urelia-slickgrid/extensions/headerMenuExtension.ts	100% <100%> (+87.58%)	⬆️
src/aurelia-slickgrid/services/filter.service.ts	12.55% <100%> (ø)	⬆️
...c/aurelia-slickgrid/extensions/extensionUtility.ts	96.43% <87.5%> (+60.72%)	⬆️
... and 3 more

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