Deduplicate transform opts in tests

[MaoShizhong]

This PR

• Uses single source of truth for transform opts in tests since they're all the same.

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Depending on what gets approved and merged with #95, #96 or #99, and in what order, I'll amend PRs as needed since the other two still use the original opts object literal.

[christina-de-martinez]

Thanks so much for all these PRs @MaoShizhong !! Looks like there's a merge conflict now, like you expected

[MaoShizhong]

@christina-de-martinez All cleaned up. I'll sort out #99 after this one's merged since it'll be more straightforward to resolve.