With Process.setEnableProcessTracing true

bad_test_execution.cs

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace TestAsyncLocal
{
    class Program
    {
        static AsyncLocal<Dictionary<string, string>> fake_data = new AsyncLocal<Dictionary<string, string>>();

        static Dictionary<string, string> getDataDict()
        {
            if (fake_data.Value == null)
            {
                Console.WriteLine("Init fake_data");
                fake_data.Value = new Dictionary<string, string>();
            }
            else
            {
                Console.WriteLine("fake_data is already initialized"); 
            }
            return fake_data.Value;
        }

        static async Task Main(string[] args)
        {
            await AsyncExecuteAllTests();
            Console.ReadKey();
            // Output:
            // Init fake_data
            // fake_data is already initialized
            // fake_data is already initialized

            // Summary: Both tests work with common dictionary
        }

        static async Task AsyncExecuteAllTests()
        {
            // When we execute Process.setEnableProcessTracing true
            getDataDict();

            //execute tests
            var t1 = AsyncTest1();
            var t2 = AsyncTest2();

            // Await both tests
            await t1;
            await t2;
        }

        static async Task AsyncTest1()
        {
            await Task.Delay(100);
            // Some test with withFakeContext
            getDataDict();
            await Task.Delay(100);
        }

        static async Task AsyncTest2()
        {
            await Task.Delay(100);
            // Some test with withFakeContext
            getDataDict();
            await Task.Delay(100);
        }
    }
}