Refactor tests

[ErikDanielsson]

Refactored test directory:

• The test for the different nf-core modules subcommands are now placed in individual files
• The last few tests that depend the number of passed/warned/failed tests are now replaced with inequalities, e.g.:
  assert len(self.passed) == 37 ==> assert len(self.passed) > 0.
• Renamed the test in lint/modules_json.py.

Partially resolves #1158.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #1166 (b737414) into dev (5e9e33c) will increase coverage by 1.17%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev    #1166      +/-   ##
==========================================
+ Coverage   69.22%   70.40%   +1.17%     
==========================================
  Files          50       48       -2     
  Lines        5232     5112     -120     
==========================================
- Hits         3622     3599      -23     
+ Misses       1610     1513      -97     

Impacted Files	Coverage Δ
nf_core/lint/__init__.py	74.78% <0.00%> (-0.32%)	⬇️
nf_core/lint/files_exist.py	81.81% <0.00%> (ø)
nf_core/lint/conda_dockerfile.py
nf_core/lint/conda_env_yaml.py
nf_core/modules/test_yml_builder.py	45.98% <0.00%> (+0.29%)	⬆️
nf_core/lint/readme.py	79.31% <0.00%> (+26.36%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5e9e33c...b737414. Read the comment docs.

[KevinMenden]

Nice, thanks!
This looks great 👍

[ErikDanielsson]

Thanks @KevinMenden!