test: add UT for undo module

[maple525866]

• I have read the CONTRIBUTING.md guidelines.
• I have registered the PR changes.

Ⅰ. Describe what this PR did

add UT for undo module

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.34%. Comparing base (61e375f) to head (4208758).

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #7757      +/-   ##
============================================
+ Coverage     66.17%   66.34%   +0.16%     
+ Complexity      994      992       -2     
============================================
  Files          1323     1323              
  Lines         50155    50155              
  Branches       5928     5928              
============================================
+ Hits          33190    33273      +83     
+ Misses        14053    13963      -90     
- Partials       2912     2919       +7     

see 18 files with indirect coverage changes

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