MsBuild TaSk

msbuild.proj

<?xml version="1.0" encoding="utf-8" ?>
<Project DefaultTargets="Test" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" >
  <UsingTask TaskName="MyMsBuildTask.RunWP7UnitTestsInEmulator"
      AssemblyFile="MyMsBuildTask.dll"/>

  <PropertyGroup>
    <SourceFilesPath>$(MSBuildProjectDirectory)</SourceFilesPath>

  </PropertyGroup>

  <ItemGroup>
    <SolutionItemsToBuild Include="$(SourceFilesPath)\**\*.sln" />
  </ItemGroup>

  <Target Name="Build">
    <MSBuild Projects="%(SolutionItemsToBuild.Identity)" Targets="Build"/>
  </Target>

  <Target Name="Test" DependsOnTargets="Build">
    <RunWP7UnitTestsInEmulator NumberOfMilliSecondsToProcess="50000"
        PathToUnitTestXapFile="$(SourceFilesPath)\(your test project).xap"
        ProductGuid="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" />
  </Target>
</Project>