In principle, I would prefer to declare my usings in C#. I don't love to edit my
csproj files, but Martin remembered me that I can do it in a
Directory.Build.props file (if you want to know more about this file, take a look at this post that I've written to see the potential).
The beauty of it is that if you place
Directory.Build.props in the root folder that contains your source code, when MSBuild runs will add to every project the properties defined in the
Directory.Build.props. So, if you want to do it Solution wise or even only for your Test folder, you can do it.
I will be using
Directory.Build.props for sure. At least until we see a new standard way to declare global usings emerging in the community.
I hope that this was useful! To get more tips like this, follow me on Twitter (@gsferreira) and let's keep in touch!