To carry on the CodePlex discussion with @MattGertz and @KevinRansom, I'm still seeing many unit test failures on the GitHub master branch. I assume you are still working on this as part of the move to GitHub but I thought it might be helpful to report the issues I'm seeing right now.

I created a clean VS2015 CTP5 machine on Azure today, installed the CTP SDK, cloned Roslyn (at the time master's HEAD was 7fed8e8) and ran msbuild /m BuildAndTest.proj /p:DeployExtension=false.

Here are the problems I saw:

Build Failure

C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v14.0\VSSDK\Microsoft.VsSDK.targets(760,5):     error : CreatePkgDef : error : FileLoadException: Could not load file or assembly 'OpenSourceDebug,    Version=42.42.42.42, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its    dependencies. Strong name validation failed. (Exception from HRESULT: 0x8013141A)   [c:\dev\roslyn\Src\Tools\Source\OpenSourceDebug\OpenSourceDebug.csproj]

I ran sn -Vr *,31bf3856ad364e35 to work around this.

Crashes during test run

When the tests run, for every test tries to launch the command line compiler (and there are many), a crash dialog pops up saying that "VBCSCompiler has stopped working" or "csc.exe has stopped working". I also got an error saying:

Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'csc,Version=42.42.42.42, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. Strong name validation failed. (Exception from HRESULT: 0x8013141A) ---

Again, this seems to be related to strong name validations, and this time the fact I SN -Vr'ed that same public key didn't help. To get past the crash dialogs, I manually deleted Roslyn.Compilers.CompilerServer.UnitTests.dll Roslyn.Compilers.CSharp.CommandLine.UnitTests.dll and Roslyn.Compilers.VisualBasic.CommandLine.UnitTests.dll, and then ran:
msbuild /target:test /m BuildAndTest.proj /p:DeployExtension=false

Remaining unit test failures

Finally, the resulting UnitTestResults.html file reported 2 unit test failures, while the command-line window consistently reported 39.