#14873: test for groupby.agg coercing booleans
- [x] closes #14873 
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

The referenced issue seems to be solved in the current master. So added a test for the edge case.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25327?src=pr&el=h1) Report
> Merging [#25327](https://codecov.io/gh/pandas-dev/pandas/pull/25327?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4be995c13452766da48a82f3ecd0b5a24e48f526?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/25327/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25327?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25327   +/-   ##
=======================================
  Coverage   91.72%   91.72%           
=======================================
  Files         173      173           
  Lines       52831    52831           
=======================================
  Hits        48458    48458           
  Misses       4373     4373
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.28% <ø> (ø)` | :arrow_up: |
| #single | `41.72% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25327?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/25327?src=pr&el=footer). Last update [4be995c...0e485c2](https://codecov.io/gh/pandas-dev/pandas/pull/25327?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/25327?src=pr&el=h1) Report
> Merging [#25327](https://codecov.io/gh/pandas-dev/pandas/pull/25327?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4a20d5b9e526435a53b7cb1dc0a819299d31f040?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/25327/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25327?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25327   +/-   ##
=======================================
  Coverage   91.73%   91.73%           
=======================================
  Files         173      173           
  Lines       52839    52839           
=======================================
  Hits        48472    48472           
  Misses       4367     4367
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.29% <ø> (ø)` | :arrow_up: |
| #single | `41.72% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25327?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/25327?src=pr&el=footer). Last update [4a20d5b...14f81a9](https://codecov.io/gh/pandas-dev/pandas/pull/25327?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Hello @TrigonaMinima! Thanks for updating the PR.



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

##### Comment last updated on February 16, 2019 at 20:44 Hours UTC thanks @TrigonaMinima 