Centralize and de-duplicate comparison and arith tests

[jbrockmendel]

These are almost all cut/paste moving tests to the appropriate places. Two exceptions:

• Some "TODO: de-duplicate this with that" notes (mostly to myself)
• TestTimedeltaIndexArithmetic.test_numeric_compat badly needed to be split into more specific tests, so that is done here.

[pep8speaks]

Hello @jbrockmendel! Thanks for updating the PR.

Cheers ! There are no PEP8 issues in this Pull Request. 🍻

Comment last updated on January 19, 2018 at 18:52 Hours UTC

[codecov]

Codecov Report

Merging #19317 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #19317      +/-   ##
==========================================
- Coverage   91.53%    91.5%   -0.03%     
==========================================
  Files         150      150              
  Lines       48738    48738              
==========================================
- Hits        44611    44599      -12     
- Misses       4127     4139      +12

Flag	Coverage Δ
#multiple	89.87% <ø> (-0.03%)	⬇️
#single	41.72% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/plotting/_converter.py	65.22% <0%> (-1.74%)	⬇️

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[jreback]

thanks.

are we missing a pandas/tests/indexes/period/test_artithmetic.py?

actually there is one, I guess nothing to move there