Update test run command to get more accurate coverage.

[lsetiawan]

This PR fixes caching and also updates the run test command so it can give an accurate assessment of test coverage, which should be around 76%.

[codecov-commenter]

Codecov Report

Merging #411 (17a5b17) into dev (5c100f4) will increase coverage by 73.24%.
The diff coverage is 95.58%.

@@            Coverage Diff             @@
##             dev     #411       +/-   ##
==========================================
+ Coverage   2.21%   75.46%   +73.24%     
==========================================
  Files         35       35               
  Lines       3019     3032       +13     
==========================================
+ Hits          67     2288     +2221     
+ Misses      2952      744     -2208     

Flag	Coverage Δ
unittests	75.46% <95.58%> (+73.24%)	⬆️

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Impacted Files	Coverage Δ
echopype/preprocess/api.py	87.17% <ø> (+87.17%)	⬆️
echopype/utils/io.py	84.21% <95.16%> (+58.28%)	⬆️
echopype/convert/api.py	86.40% <100.00%> (+86.40%)	⬆️
echopype/convert/utils/ek_raw_io.py	42.61% <100.00%> (+42.61%)	⬆️
echopype/echodata/echodata.py	75.20% <100.00%> (+40.24%)	⬆️
echopype/convert/utils/ek_date_conversion.py	33.33% <0.00%> (+33.33%)	⬆️
echopype/convert/parse_ek80.py	50.00% <0.00%> (+50.00%)	⬆️
... and 28 more

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