Changing from serializing ProcessStartInfo to our own TestStartInfo class, because serializing ProcessStartInfo doesn't really work cross-platform due to unsupported properties.

src/dotnet/commands/dotnet-test/CommandTestRunnerExtensions.cs

@@ -1,16 +1,19 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-using System.Diagnostics;
 using Microsoft.DotNet.Cli.Utils;
 
 namespace Microsoft.DotNet.Tools.Test
 {
     public static class CommandTestRunnerExtensions
     {
-        public static ProcessStartInfo ToProcessStartInfo(this ICommand command)
+        public static TestStartInfo ToTestStartInfo(this ICommand command)
         {
-            return new ProcessStartInfo(command.CommandName, command.CommandArgs);
+            return new TestStartInfo
+            {
+                FileName = command.CommandName,
+                Arguments = command.CommandArgs
+            };
         }
     }
 }

src/dotnet/commands/dotnet-test/TestRunners/ITestRunner.cs

@@ -1,16 +1,12 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-using System.Collections.Generic;
-using System.Diagnostics;
-using Microsoft.Extensions.Testing.Abstractions;
-
 namespace Microsoft.DotNet.Tools.Test
 {
     public interface ITestRunner
     {
         void RunTestCommand();
 
-        ProcessStartInfo GetProcessStartInfo();
+        TestStartInfo GetProcessStartInfo();
     }
 }

src/dotnet/commands/dotnet-test/TestRunners/TestRunner.cs

@@ -29,11 +29,11 @@ namespace Microsoft.DotNet.Tools.Test
             ExecuteRunnerCommand();
         }
 
-        public ProcessStartInfo GetProcessStartInfo()
+        public TestStartInfo GetProcessStartInfo()
         {
             var command = CreateTestRunnerCommand();
 
-            return command.ToProcessStartInfo();
+            return command.ToTestStartInfo();
         }
 
         private void ExecuteRunnerCommand()

src/dotnet/commands/dotnet-test/TestStartInfo.cs

@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.DotNet.Tools.Test
+{
+    public class TestStartInfo
+    {
+        public string FileName { get; set; }
+
+        public string Arguments { get; set; }
+    }
+}

test/dotnet-test.UnitTests/GivenATestExecutionGetTestRunnerProcessStartInfoMessageHandler.cs

@@ -19,7 +19,7 @@ namespace Microsoft.Dotnet.Tools.Test.Tests
 
         private GetTestRunnerProcessStartInfoMessageHandler _testGetTestRunnerProcessStartInfoMessageHandler;
         private Message _validMessage;
-        private ProcessStartInfo _processStartInfo;
+        private TestStartInfo _testStartInfo;
 
         private Mock<ITestRunner> _testRunnerMock;
         private Mock<ITestRunnerFactory> _testRunnerFactoryMock;
@@ -42,10 +42,14 @@ namespace Microsoft.Dotnet.Tools.Test.Tests
             _dotnetTestMock.Setup(d => d.State).Returns(DotnetTestState.VersionCheckCompleted);
             _dotnetTestMock.Setup(d => d.PathToAssemblyUnderTest).Returns(AssemblyUnderTest);
 
-            _processStartInfo = new ProcessStartInfo("runner", "arguments");
+            _testStartInfo = new TestStartInfo
+            {
+                FileName = "runner",
+                Arguments = "arguments"
+            };
 
             _testRunnerMock = new Mock<ITestRunner>();
-            _testRunnerMock.Setup(t => t.GetProcessStartInfo()).Returns(_processStartInfo);
+            _testRunnerMock.Setup(t => t.GetProcessStartInfo()).Returns(_testStartInfo);
 
             _testRunnerFactoryMock = new Mock<ITestRunnerFactory>();
             _testRunnerFactoryMock
@@ -128,8 +132,8 @@ namespace Microsoft.Dotnet.Tools.Test.Tests
         {
             _adapterChannelMock.Setup(r => r.Send(It.Is<Message>(m =>
                 m.MessageType == TestMessageTypes.TestExecutionTestRunnerProcessStartInfo &&
-                m.Payload.ToObject<ProcessStartInfo>().FileName == _processStartInfo.FileName &&
+                m.Payload.ToObject<ProcessStartInfo>().FileName == _testStartInfo.FileName &&
-                m.Payload.ToObject<ProcessStartInfo>().Arguments == _processStartInfo.Arguments))).Verifiable();
+                m.Payload.ToObject<ProcessStartInfo>().Arguments == _testStartInfo.Arguments))).Verifiable();
 
             _testGetTestRunnerProcessStartInfoMessageHandler.HandleMessage(
                     _dotnetTestMock.Object,

test/dotnet-test.UnitTests/GivenThatWeWantToRunTests.cs

@@ -19,7 +19,7 @@ namespace Microsoft.Dotnet.Tools.Test.Tests
 
             dotnetTestMessageScenario.TestRunnerMock
                 .Setup(t => t.GetProcessStartInfo())
-                .Returns(new ProcessStartInfo())
+                .Returns(new TestStartInfo())
                 .Verifiable();
 
             dotnetTestMessageScenario.AdapterChannelMock