[tests] add tests in inplace_update_test.go

[patilpratik1905]

Ⅰ. Describe what this PR does

This PR adds unit tests to improve coverage of the inplace_update_test used for generating and applying Pod patch updates.
Added the below functions

• TestDefaultGeneratePatchBodyFunc
  Validates patch generation by comparing Sandbox and Pod container images, ensuring patches are created only when required and correctly handle partial updates, sidecars, and empty container specs.

• TestNewInPlaceUpdateControl
  Verifies proper initialization of the in-place update controller with different patch function configurations, ensuring the client and patch function are set correctly.

• TestInPlaceUpdateControl_Update_WithCustomPatchFunc
  Ensures the update operation safely returns a no-op when a custom patch function produces an empty patch, without errors or unnecessary API calls.

Ⅱ. Does this pull request fix one issue?

No

Ⅲ. Describe how to verify it

Ran make test to check coverage of file

• Before :

• After :

Ⅳ. Special notes for reviews

• Changes are kept minimal and scoped to inplace_update_test.go for easier review.
• Please let me know if the updated test expectations should be adjusted further to match intended behavior.

[kruise-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.93%. Comparing base (10d5f54) to head (7c118bc).
⚠️ Report is 157 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #115      +/-   ##
==========================================
+ Coverage   48.71%   51.93%   +3.22%     
==========================================
  Files          85       87       +2     
  Lines        4701     4785      +84     
==========================================
+ Hits         2290     2485     +195     
+ Misses       2208     2089     -119     
- Partials      203      211       +8     

Flag	Coverage Δ
unittests	51.93% <ø> (+3.22%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[kruise-bot]

@patilpratik1905: PR needs rebase.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.