test: add unit test for Tabs component

[mortalYoung]

Description

• add unit test for Tabs component
• export className for testing

[codecov]

Codecov Report

Merging #339 (1822936) into main (a2bb68c) will increase coverage by 1.30%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
+ Coverage   51.65%   52.95%   +1.30%     
==========================================
  Files         173      173              
  Lines        4600     4604       +4     
  Branches     1013     1016       +3     
==========================================
+ Hits         2376     2438      +62     
+ Misses       2196     2138      -58     
  Partials       28       28              

Impacted Files	Coverage Δ
src/components/tabs/index.tsx	100.00% <100.00%> (+22.22%)	⬆️
src/workbench/problems/paneView/index.tsx	40.00% <0.00%> (+16.00%)	⬆️
src/components/tabs/tab.tsx	100.00% <0.00%> (+60.46%)	⬆️
src/components/tabs/tabExtra.tsx	100.00% <0.00%> (+100.00%)	⬆️

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