Can't run tests with XUnit in parallel in Visual Studio

I have two classes TestClass1, TestClass2

I have set MaxParallel threads through assembly in AssemblyInfo.cs file in my test project:
[assembly: Xunit.CollectionBehaviorAttribute (MaxParallelThreads = 4)]
Link Set Max Parallel Threads

I have installed xunit-2.0.0-beta4-build2738 (Prerelease). Also installed Xunit runner to find tests.

From my knowledge and research, it is reported that Xunit does not run tests on the same collection in parallel. Link Using Test Collections in xUnit.net v2 , so I used different collections for both classes below.

Visual Studio 2013 finds my tests, but when I run all the tests, it still runs the tests one at a time. I want them to run in parallel.

If anyone can help, that would be great!

My code is below:
Namespace1

namespace name1
{
   public class MFixture
   {

   }

   [CollectionDefinition("Test1")]
   public class CollectionClass : ICollectionFixture<MFixture>
   {

   }

   [Collection("Test1")]
   public class TestClass1
   {
      // variables
      public TestClass1()
      {
         //code
      }

      [Fact]
      public void method1()
      {
          //code
      }

      [Fact]
      public void method2()
      {
        //code
      }
   }
}

      

        
        
        
      

    

Namespace2

namespace name2
{
   public class MFixture1
   {

   }

   [CollectionDefinition("Test2")]
   public class CollectionClass1 : ICollectionFixture<MFixture1>
   {

   }

   [Collection("Test2")]
   public class TestClass2
   {
      // variables
      public TestClass2()
      {
         //code
      }

      [Fact]
      public void method12()
      {
        //code
      }

      [Fact]
      public void method22(){
      {
         //code
      }
   }
}

      

        
        
        
      

    

Other links
How to run Selenium tests in parallel with xUnit
XUnit.net attributes XUnit.net
problems