~Finish Collecting Arithmetic Tests
De-duplicate fixtures and put nearly all of them in conftest
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22350?src=pr&el=h1) Report
> Merging [#22350](https://codecov.io/gh/pandas-dev/pandas/pull/22350?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/98fb53ca2d64658749e9f182b391002ef3500c1b?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/22350/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22350?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22350   +/-   ##
=======================================
  Coverage   92.04%   92.04%           
=======================================
  Files         169      169           
  Lines       50787    50787           
=======================================
  Hits        46745    46745           
  Misses       4042     4042
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.45% <ø> (ø)` | :arrow_up: |
| #single | `42.29% <ø> (ø)` | :arrow_up: |


------

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> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22350?src=pr&el=footer). Last update [98fb53c...25ed1e8](https://codecov.io/gh/pandas-dev/pandas/pull/22350?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you rebase Rebased.  After this the tests are pretty much all consolidated, so the next planned follow-up is to paramatrize/de-duplicate.

Also since#22390 just went in, upcoming PR to fix _most_ of the outstanding xfails @jbrockmendel : Have you addressed all of the comments here?  I know you were waiting on @jreback to review this again, but at first glance, I can't tell if you have addressed everything he mentioned earlier. > Have you addressed all of the comments here? 

I think so, yes.  But since this is a big enough PR that it is hard to keep track, I made #22559 as a subset of this in the hopes it would be easier in smaller pieces. > I think so, yes.

@jbrockmendel : What about this one [here](https://github.com/pandas-dev/pandas/pull/22350#discussion_r210548778)?  Just double checking! 🙂 

So should we be reviewing / merging this?  Or should we go after #22559 first? > What about this one here? Just double checking!

The suggestion on the fixture names was to stop fiddling for now and address in the next round.  Since there were multiple comments about fixture names, its easy to lose track when one response is aimed at multiple comments.

> So should we be reviewing / merging this? Or should we go after #22559 first?

Best case would be that everyone is happy here and #22559 is unnecessary.  If this is going to be a slog, then I'd like to get #22559 in as this is a blocker for other work. ping @jreback - could you review this again? can you rebsae Closing in favor of #22645.