add nodepool controoller unit test

[luc99hen]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line: /kind bug /kind documentation

/kind enhancement

/kind good-first-issue /kind feature /kind question /kind design /sig ai /sig iot /sig network /sig storage /sig storage

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes # https://github.com/openyurtio/yurt-app-manager/issues/73

Special notes for your reviewer:

This PR add unit tests for nodepool controller and some related utils function. To improve the test coverage, some controller code are refactored for better testability.

Does this PR introduce a user-facing change?

no

other Note

[openyurt-bot]

@luc99hen: GitHub didn't allow me to assign the following users: your_reviewer.

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In response to [this](https://github.com/openyurtio/yurt-app-manager/pull/89): > > > >#### What type of PR is this? >> Uncomment only one ` /kind <>` line, hit enter to put that in a new line, and remove leading whitespace from that line: >> /kind bug >> /kind documentation >/kind enhancement >> /kind good-first-issue >> /kind feature >> /kind question >> /kind design >> /sig ai >> /sig iot >> /sig network >> /sig storage >> /sig storage > > > >#### What this PR does / why we need it: > >#### Which issue(s) this PR fixes: > >Fixes # https://github.com/openyurtio/yurt-app-manager/issues/73 > >#### Special notes for your reviewer: > >This PR add unit tests for nodepool controller and some related utils function. To improve the test coverage, some controller code are refactored for better testability. > >#### Does this PR introduce a user-facing change? > >```release-note > >``` > >#### other Note > > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[luc99hen]

/assign @kadisi

[codecov[bot]]

Codecov Report

Merging #89 (d09f5c4) into master (fe8491b) will increase coverage by 7.57%. The diff coverage is 72.00%.

@@            Coverage Diff             @@
##           master      #89      +/-   ##
==========================================
+ Coverage    7.78%   15.36%   +7.57%     
==========================================
  Files          17       18       +1     
  Lines        1901     1953      +52     
==========================================
+ Hits          148      300     +152     
+ Misses       1724     1617     -107     
- Partials       29       36       +7     

Flag	Coverage Δ
unittests	15.36% <72.00%> (+7.57%)	:arrow_up:

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

Impacted Files	Coverage Δ
...r/controller/nodepool/nodepool_enqueue_handlers.go	0.00% <ø> (ø)
...manager/controller/nodepool/nodepool_controller.go	56.41% <71.62%> (+39.58%)	:arrow_up:
...g/yurtappmanager/util/gate/custom_resource_gate.go	70.83% <100.00%> (ø)

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[rambohe-ch]

/lgtm /approve

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: luc99hen, rambohe-ch

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/openyurtio/yurt-app-manager/blob/master/OWNERS)~~ [rambohe-ch] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment