feat: add unit tests for manager handlers

[BruceAko]

Description

Add unit tests for manager handlers.

Related Issue

fix #2705

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[BruceAko]

@gaius-qi So far I've written unit tests for application.go, could you please review this part of the code so that I can make sure I'm writing the unit tests in the right way? Thank you very much :)

[gaius-qi]

@gaius-qi So far I've written unit tests for application.go, could you please review this part of the code so that I can make sure I'm writing the unit tests in the right way? Thank you very much :)

@BruceAko I think it is good！

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.78%. Comparing base (11ff4d4) to head (ab8a0af).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3202      +/-   ##
==========================================
+ Coverage   52.06%   52.78%   +0.72%     
==========================================
  Files         173      192      +19     
  Lines       19382    20341     +959     
==========================================
+ Hits        10091    10738     +647     
- Misses       8585     8800     +215     
- Partials      706      803      +97     

Flag	Coverage Δ
unittests	52.78% <ø> (+0.72%)	⬆️

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

see 22 files with indirect coverage changes

[gaius-qi]

@BruceAko It is also draft. Have you finished PR?

[BruceAko]

@gaius-qi I have finished PR now. Please take a look.

[gaius-qi]

@BruceAko Can you add unit tests for �handlers.go in next PR? Thx

[BruceAko]

@BruceAko Can you add unit tests for �handlers.go in next PR? Thx

@gaius-qi Okay. And I fixed the above changes in two new commits, PTAL.

[gaius-qi]

LGTM