[Spike - Developer Guide] Writing test cases

[GPortas]

Overview of the Feature Request

Create the second section of the developer guide: Writing test cases

This issue is a spike created from https://github.com/IQSS/dataverse-frontend/issues/304 to narrow the scope a little and be able to better prioritize it.

What kind of user is the feature intended for?

Developers.

What inspired the request?

• https://github.com/IQSS/dataverse-frontend/issues/304

What existing behavior do you want changed?

N/A

Any brand new behavior do you want to add to Dataverse?

N/A

Any open or closed issues related to this feature request?

• https://github.com/IQSS/dataverse-frontend/issues/304