MSBuildForUnity doesn't resolve asmdef references to nunit.framework.dll

Using Unity 2019.2.17f1 with MSB4U, I am unable to build test asmdefs that contain references to UnityTest classes and the nunit.framework.dll

The UnityTest class may require additional references to UPM packages and may be fixable on my side. It seems like the nunit.framework.dll should be a managed dll that MSB4U resolves references for.