RoslynTester

This release fixes issues which caused VB.NET and C# tests to give false positive/negatives due to incorrect comparison.

Furthermore: tests will now fail if they include code that can't be compiled -- previously they would pass silently. We've already established that this caused several hidden issues in our tests in the VSDiagnostics project.
Note that this is a breaking change with the default test package implementation as provided by Microsoft in the solution template.