Enhance unit test for explore

[wonjuleee]

Summary

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (817b44e) 80.58% compared to head (ae7e3cf) 80.60%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1266      +/-   ##
===========================================
+ Coverage    80.58%   80.60%   +0.01%     
===========================================
  Files          270      270              
  Lines        30347    30347              
  Branches      5904     5904              
===========================================
+ Hits         24456    24462       +6     
+ Misses        4507     4504       -3     
+ Partials      1384     1381       -3     

Flag	Coverage Δ
ubuntu-20.04_Python-3.8	80.59% <ø> (+<0.01%)	⬆️
windows-2022_Python-3.8	80.57% <ø> (?)

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[sooahleex]

Looks good to me.