test(tabs): add unit tests

[joshka]

No description provided.

[codecov]

Codecov Report

Merging #439 (d27cb56) into main (ad3413e) will increase coverage by 1.17%.
Report is 3 commits behind head on main.
The diff coverage is 75.96%.

@@            Coverage Diff             @@
##             main     #439      +/-   ##
==========================================
+ Coverage   89.25%   90.42%   +1.17%     
==========================================
  Files          40       40              
  Lines       10767    11081     +314     
==========================================
+ Hits         9610    10020     +410     
+ Misses       1157     1061      -96     

Files Changed	Coverage Δ
src/widgets/tabs.rs	87.25% <75.96%> (+12.25%)	⬆️

... and 4 files with indirect coverage changes