TST: add back test_generic.py, accid removed in the big reorg
somehow this file got removed a while back. I split it up a bit in any event. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=h1) Report
> Merging [#18114](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8388a47b7b09d345f463fe5fe91f32e87f7bb550?src=pr&el=desc) will **increase** coverage by `0.15%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18114/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18114      +/-   ##
==========================================
+ Coverage   91.25%   91.41%   +0.15%     
==========================================
  Files         163      163              
  Lines       50124    50126       +2     
==========================================
+ Hits        45742    45822      +80     
+ Misses       4382     4304      -78
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.22% <100%> (+0.17%)` | :arrow_up: |
| #single | `40.32% <0%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.72% <100%> (+3.3%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.05%)` | :arrow_down: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `94.54% <0%> (+0.07%)` | :arrow_up: |
| [pandas/core/panel.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcGFuZWwucHk=) | `97.28% <0%> (+0.28%)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.2% <0%> (+1.81%)` | :arrow_up: |
| [pandas/core/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tbW9uLnB5) | `93% <0%> (+1.82%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18114?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/18114?src=pr&el=footer). Last update [8388a47...62e616e](https://codecov.io/gh/pandas-dev/pandas/pull/18114?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/18114?src=pr&el=h1) Report
> Merging [#18114](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8441f0279b066a596e0d019335cc7cbe3bfbcec1?src=pr&el=desc) will **increase** coverage by `0.1%`.
> The diff coverage is `83.33%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18114/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##           master   #18114     +/-   ##
=========================================
+ Coverage   91.28%   91.39%   +0.1%     
=========================================
  Files         163      163             
  Lines       50130    50132      +2     
=========================================
+ Hits        45761    45817     +56     
+ Misses       4369     4315     -54
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.2% <83.33%> (+0.12%)` | :arrow_up: |
| #single | `40.33% <8.33%> (-0.06%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.72% <83.33%> (+3.3%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.38% <0%> (-1.82%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.05%)` | :arrow_down: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `94.54% <0%> (+0.07%)` | :arrow_up: |
| [pandas/core/panel.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcGFuZWwucHk=) | `97.28% <0%> (+0.28%)` | :arrow_up: |
| [pandas/core/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tbW9uLnB5) | `93% <0%> (+1.82%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18114?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/18114?src=pr&el=footer). Last update [8441f02...a63f66d](https://codecov.io/gh/pandas-dev/pandas/pull/18114?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
