What supporting test infrastructure can we share?

[michaelcfanning]

Ideas include:

1. share fix-all test process
2. define common/consistent unit test patterns (using embedded strings? what about driving analysis from loose files to assist with editing test cases?)
3. pull together common test cases (with a special emphasis on negative patterns)
4. provide a 'reference repo' and automation that applies submitted analyzers in a repo branch and provides some baselining/diffing capabilities
5. provide performance testing automation
6. Roslyn diagnostics analyzers (mentioned previously): analyzers must be clean for these checks to be the best they can be