Add groupByDate tests

[Clebal]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 1877236689

• 21 of 21 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.9%) to 72.537%

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Totals
Change from base Build 1864689908:	1.9%
Covered Lines:	1282
Relevant Lines:	1664

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💛 - Coveralls

[VictorVelarde]

It would be probably easier to read if your ARGS is a dictionary, not array, and you do

const params = { features, operation, date, grouping }
// ...
params.grouping = XXX
// ...
executeGroupByDateFnTests(params, RESULT);

[Clebal]

Much better! I changed it :)

[VictorVelarde]

LGTM