Describe how to get tests to run

CONTRIBUTING.md

@@ -12,3 +12,26 @@ with any additional questions or comments.
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+
+## Building
+
+To build this project, first run the `init.ps1` or `init.cmd` scripts in the root of the repo.
+
+### Running tests
+
+Most test runners will shadow copy assemblies, which the desktop CLR won't do for "public signed"
+assemblies. To run tests, disable shadow copying in your test runner.
+
+Alternatively you can disable public signing in favor of delay signing by setting
+the `SignType` environment variable to `mock`.
+This may cause the CLR to reject the assembly because it is delay signed, so you can
+tell the CLR to skip delay sign verification of this assembly using this command
+from an elevated Visual Studio Developer Command Prompt:
+
+```
+sn -Vr Microsoft.VisualStudio.Validation,b03f5f7f11d50a3a
+```
+
+Then restart your test runner process and rebuild the project
+(with the SignType env var set as described above).
+The tests should run.