[AIRFLOW-5732] Add unit test for the version command

[sekikn]

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Jira

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  • https://issues.apache.org/jira/browse/AIRFLOW-5732
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Description

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This PR adds a unit test for the airflow version command.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

test_cli_version in tests/core.py

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  6. Body explains "what" and "why", not "how"

Documentation

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[codecov-io]

Codecov Report

Merging #6401 into master will decrease coverage by 0.3%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6401      +/-   ##
==========================================
- Coverage   80.61%   80.31%   -0.31%     
==========================================
  Files         626      626              
  Lines       36217    36217              
==========================================
- Hits        29196    29086     -110     
- Misses       7021     7131     +110

Impacted Files	Coverage Δ
airflow/kubernetes/volume_mount.py	44.44% <0%> (-55.56%)	⬇️
airflow/kubernetes/volume.py	52.94% <0%> (-47.06%)	⬇️
airflow/kubernetes/pod_launcher.py	45.25% <0%> (-46.72%)	⬇️
airflow/kubernetes/kube_client.py	33.33% <0%> (-41.67%)	⬇️
...rflow/contrib/operators/kubernetes_pod_operator.py	70.14% <0%> (-28.36%)	⬇️
airflow/bin/cli.py	66.31% <0%> (+0.1%)	⬆️

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[mik-laj]

I'm afraid this test is in the wrong place. tests/cli/test_cli.py is a better file.

I am also afraid of sys.stdout mocking. Python has a special mechanism for this. 
https://github.com/sekikn/incubator-airflow/blob/9ff0c4f79a009618215a2af60418f664168456f4/tests/cli/test_cli.py#L344-L352

[sekikn]

Thanks for the comment @mik-laj!

I'm afraid this test is in the wrong place. tests/cli/test_cli.py is a better file.

The reason that I added the new test to test/core.py was it has many cli-related tests in its TestCli class. I have no objection to move the new test into tests/cli/test_cli.py, but is there any criteria to put a new cli-related test into it (or should we basically use tests/cli/test_cli.py in the future)?

I am also afraid of sys.stdout mocking. Python has a special mechanism for this.

I didn't use contextlib.redirect_stdout because of concern for the compatibility with Python2, but I've just noticed we're going to drop it on the master branch. I'll address it on another PR, thanks :)