chore: tweak unittest

[zhaoyongjie]

🏠 Internal
tweak unittest to prepare monorepo

1. import from source code instead lib
2. fix flaky test
3. export variable used by Superset

[vercel]

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[codecov]

Codecov Report

Merging #1460 (051e063) into master (0ca4f73) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1460   +/-   ##
=======================================
  Coverage   30.62%   30.62%           
=======================================
  Files         499      499           
  Lines       10048    10048           
  Branches     1699     1699           
=======================================
  Hits         3077     3077           
  Misses       6723     6723           
  Partials      248      248           

Impacted Files	Coverage Δ
plugins/plugin-chart-echarts/src/types.ts	100.00% <ø> (ø)

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[kgabryje]

LGTM

[villebro]

LGTM