fix: simplify test cases by directly setting CACHE_TMP_DIR mock value

[darkrush]

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Motivation

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Modification

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BC-breaking (Optional)

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Use cases (Optional)

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Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

@@            Coverage Diff             @@
##              dev     #302      +/-   ##
==========================================
+ Coverage   89.70%   89.88%   +0.17%     
==========================================
  Files          82       82              
  Lines        5556     5556              
==========================================
+ Hits         4984     4994      +10     
+ Misses        572      562      -10     

see 6 files with indirect coverage changes

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