ENH: snapshot testing of dataframes
#### Is your feature request related to a problem?

When testing dataframe manipulating functions defining explicit expected dataframes takes a lot of time.

#### Describe the solution you'd like

I've used [snapshottest](https://github.com/syrusakbary/snapshottest) to test GraphQl APIs. The same approach could be implemented in a pytest plugin for pandas as well.

#### API breaking implications

[this should provide a description of how this feature will affect the API]

#### Describe alternatives you've considered

[this should provide a description of any alternative solutions or features you've considered]

#### Additional context

[add any other context, code examples, or references to existing implementations about the feature request here]

```python
# Your code here, if applicable

```
