Refactor existing tests

[vinnamkim]

This should be merged after #802.

Summary

• Split our existing tests into unit, integration/cli, and e2e (empty, TODO)
• Add some common utils functions to the tests.

How to test

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues

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) 2021 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov-commenter]

Codecov Report

Base: 83.95% // Head: 83.93% // Decreases project coverage by -0.03% ⚠️

Coverage data is based on head (d32c686) compared to base (5daaa9e).
Patch coverage: 75.00% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #803      +/-   ##
===========================================
- Coverage    83.95%   83.93%   -0.03%     
===========================================
  Files          174      174              
  Lines        22923    22937      +14     
  Branches      4970     4972       +2     
===========================================
+ Hits         19245    19252       +7     
- Misses        2552     2559       +7     
  Partials      1126     1126              

Flag	Coverage Δ
macos-11_Python-3.10	83.84% <75.00%> (-0.03%)	⬇️
macos-11_Python-3.7	83.53% <73.68%> (-0.03%)	⬇️
macos-11_Python-3.8	83.77% <75.00%> (-0.03%)	⬇️
macos-11_Python-3.9	83.78% <75.00%> (-0.03%)	⬇️
ubuntu-20.04_Python-3.10	83.85% <75.00%> (-0.03%)	⬇️
ubuntu-20.04_Python-3.7	83.54% <73.68%> (-0.02%)	⬇️
ubuntu-20.04_Python-3.8	83.78% <75.00%> (-0.03%)	⬇️
ubuntu-20.04_Python-3.9	83.80% <75.00%> (-0.03%)	⬇️
windows-2019_Python-3.10	83.81% <75.00%> (-0.02%)	⬇️
windows-2019_Python-3.7	83.49% <73.68%> (-0.03%)	⬇️
windows-2019_Python-3.8	83.73% <75.00%> (-0.03%)	⬇️
windows-2019_Python-3.9	83.75% <75.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
datumaro/util/telemetry_utils.py	75.83% <54.54%> (-3.12%)	⬇️
datumaro/util/test_utils.py	89.94% <100.00%> (+0.44%)	⬆️
datumaro/util/telemetry_stub.py	80.00% <0.00%> (-6.67%)	⬇️
datumaro/components/media.py	84.61% <0.00%> (-0.30%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[wonjuleee]

looks good to me thank you!