OrderedTests.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Xunit.Abstractions;
using Xunit.Sdk;

namespace EntityTesting3
{
   [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
   public class TestPriorityAttribute : Attribute
   {
      public TestPriorityAttribute(int priority)
      {
         Priority = priority;
      }

      public int Priority { get; private set; }
   }

   public class PriorityOrderer : ITestCaseOrderer
   {
      public IEnumerable<TTestCase> OrderTestCases<TTestCase>(IEnumerable<TTestCase> testCases)
         where TTestCase : ITestCase
      {
         var sortedMethods = new SortedDictionary<int, List<TTestCase>>();

         foreach(TTestCase testCase in testCases)
         {
            int priority = 0;

            foreach(IAttributeInfo attr in testCase.TestMethod.Method.GetCustomAttributes((typeof(TestPriorityAttribute)
               .AssemblyQualifiedName)))
            {
               priority = attr.GetNamedArgument<int>("Priority");
            }

            GetOrCreate(sortedMethods, priority).Add(testCase);
         }

         foreach(var list in sortedMethods.Keys.Select(priority => sortedMethods[priority]))
         {
            list.Sort((x, y) => StringComparer.OrdinalIgnoreCase.Compare(x.TestMethod.Method.Name,
               y.TestMethod.Method.Name));

            foreach(TTestCase testCase in list)
            {
               yield return testCase;
            }
         }
      }

      static TValue GetOrCreate<TKey, TValue>(IDictionary<TKey, TValue> dictionary, TKey key) where TValue : new()
      {
         TValue result;

         if(dictionary.TryGetValue(key, out result))
         {
            return result;
         }

         result = new TValue();
         dictionary[key] = result;
         return result;
      }
   }
}