Move ExcelWriter Tests
State: closed

Because read_excel and ExcelWriter have different parametrization requirements it makes things clearer for now to separate these out.

Maybe longer term they can be more intelligently combined but for now I think this still helps clean up requirements for adding new engines

@simonjayhawkins 

Labels:
name: Testing
description: pandas testing functions or related to the test suite
name: IO Excel
description: read_excel, to_excel

Comments:
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=h1) Report
> Merging [#26740](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3937fbc5fa7d4228c65e863a24d69fa4b7cf4ec7?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26740/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26740      +/-   ##
==========================================
- Coverage   91.78%   91.77%   -0.01%     
==========================================
  Files         174      174              
  Lines       50703    50703              
==========================================
- Hits        46538    46534       -4     
- Misses       4165     4169       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.37% <ø> (ø)` | :arrow_up: |
| #single | `41.81% <ø> (-0.09%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26740/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26740/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.88% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=footer). Last update [3937fbc...cb5d640](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=h1) Report
> Merging [#26740](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3937fbc5fa7d4228c65e863a24d69fa4b7cf4ec7?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26740/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26740      +/-   ##
==========================================
- Coverage   91.78%   91.77%   -0.01%     
==========================================
  Files         174      174              
  Lines       50703    50703              
==========================================
- Hits        46538    46534       -4     
- Misses       4165     4169       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.37% <ø> (ø)` | :arrow_up: |
| #single | `41.81% <ø> (-0.09%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26740/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26740/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.88% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=footer). Last update [3937fbc...cb5d640](https://codecov.io/gh/pandas-dev/pandas/pull/26740?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

so maybe as a pre-cursor (after ok too) I would create pandas/tests/io/excel/test_excel, test_excel_writer and so on to make this much easier to grok
Yea definitely needs to be split into submodules. I can do that one next PR
ok thanks @WillAyd 

@simonjayhawkins quick look if you would. merge if ok. 
thanks @WillAyd