chore(scheduler-alpha): increase unit test coverage

[gracelu0]

Issue # (if applicable)

tracking issue: #31785

Reason for this change

Satisfy 90% unit test coverage required for developer preview (see https://github.com/cdklabs/team-internal/blob/main/docs/construct-library-lifecycle.md#exit-criteria-1)

Description of changes

Added parameterized unit tests for metric methods

Previous coverage summary:

=============================== Coverage summary ===============================
Statements   : 83.06% ( 103/124 )
Branches     : 76.19% ( 32/42 )
Functions    : 70.9% ( 39/55 )
Lines        : 83.47% ( 101/121 )
================================================================================

Current coverage summary:

=============================== Coverage summary ===============================
Statements   : 95.16% ( 118/124 )
Branches     : 83.33% ( 35/42 )
Functions    : 96.36% ( 53/55 )
Lines        : 95.86% ( 116/121 )
================================================================================

Description of how you validated changes

Unit tests pass

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: d2e23fe
• Result: SUCCEEDED
• Build Logs (available for 30 days)

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Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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