[AIRFLOW-5142] Fixed flaky cassandra test

[potiuk]

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Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-5142

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Code Quality

• Passes flake8

[potiuk]

@kaxil @BasPH -> we have a flaky cassandra test in master, so we'd better merge this fix quickly :)

[kaxil]

I still don't exactly understand why was that flaky

[mik-laj]

The data structure that does not store the order of the elements. Sometimes last element has the value A and other times the value B.

[mik-laj]

https://stackoverflow.com/a/39980744/1849502

[potiuk]

Yeah. It's all explained in discussion here: #5753 and https://stackoverflow.com/a/39980744/1849502 - we have two method calls and they are sometimes in different order because of race and the test originally checked only last call (that's how assert_called_with works). It seems it was only problem in python 3.5 (not sure why it passed originally ) because there it's not the "last" call but the one which is determined by the dictionary order as pointed by @mik-laj . Now the test correctly tests if the two upload methods were called in any order.

[turbaszek]

Interesting case! @potiuk is right, the test should assert two calls and I missed it in #5738 😔

[BasPH]

@kaxil @BasPH -> we have a flaky cassandra test in master, so we'd better merge this fix quickly :)

I was too late, but nice work 😄

[kaxil]

Thanks @potiuk & @mik-laj , I now understand that