add unit tests for Dataset

[jialudev]

What this PR does:
add unit tests for Dataset

Which issue(s) this PR fixes:

Fixes #

Type of changes
Please delete options that are not relevant.

• unit test
• 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 not work as expected)
• Documentation update

Feature/Issue validation/testing:

Please describe the tests that you ran to verify your changes and relevant result summary.

• Test A

• Test B

• Logs

Special notes for your reviewer:

Checklist:

• I have added unit/e2e tests that prove your fix is effective or that this feature works.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• I have reviewed my own code and ensured that it follows the project's style guidelines.

Release note:

[starship-github]

🚀 The StarShip CodeReviewer has been triggered with action(s): evaluate, describe, linter.

[zhendi]

LGTM

[starship-github]

The StarShip CodeReviewer was triggered but terminated because it encountered an issue: The MR state is not opened.

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