@@ -3,8 +3,10 @@
 
 using Xunit;
 
-// Process tests can conflict with each other, as they modify ambient state
-// like the console code page and environment variables
+#if TARGET_OSX
+// Retain serialization until process-management hangs under concurrent test classes on macOS are resolved.
+// https://github.com/dotnet/runtime/issues/135294
 [assembly: CollectionBehavior(CollectionBehavior.CollectionPerAssembly)]
+#endif
 
 [assembly: SkipOnPlatform(TestPlatforms.Browser, "System.Diagnostics.Process is not supported on Browser.")]
@@ -98,12 +98,18 @@ public struct SID_AND_ATTRIBUTES
     [DllImport("kernel32.dll")]
     internal static extern int GetConsoleOutputCP();
 
-    [DllImport("kernel32.dll")]
+    [DllImport("kernel32.dll", SetLastError = true)]
     internal static extern int SetConsoleCP(int codePage);
 
-    [DllImport("kernel32.dll")]
+    [DllImport("kernel32.dll", SetLastError = true)]
     internal static extern int SetConsoleOutputCP(int codePage);
 
+    [DllImport("kernel32.dll", SetLastError = true)]
+    internal static extern int FreeConsole();
+
+    [DllImport("kernel32.dll", SetLastError = true)]
+    internal static extern int AllocConsole();
+
     [DllImport("advapi32.dll")]
     internal static extern bool OpenProcessToken(SafeProcessHandle ProcessHandle, uint DesiredAccess, out SafeProcessHandle TokenHandle);
 
 
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.ComponentModel;
 using System.IO;
 using System.IO.Pipes;
 using System.Text;
@@ -18,22 +19,6 @@ public void TestChangesInConsoleEncoding()
         {
             const int ConsoleEncoding = 437;
 
-            void RunWithExpectedCodePage(int expectedCodePage)
-            {
-                Process p = CreateProcessLong();
-                p.StartInfo.RedirectStandardInput = true;
-                p.StartInfo.RedirectStandardOutput = true;
-                p.StartInfo.RedirectStandardError = true;
-                p.Start();
-
-                Assert.Equal(expectedCodePage, p.StandardInput.Encoding.CodePage);
-                Assert.Equal(expectedCodePage, p.StandardOutput.CurrentEncoding.CodePage);
-                Assert.Equal(expectedCodePage, p.StandardError.CurrentEncoding.CodePage);
-
-                p.Kill();
-                Assert.True(p.WaitForExit(WaitInMS));
-            };
-
             // Don't test this on Windows containers, as there is a known issue.
             // See https://github.com/dotnet/runtime/issues/42000 for more details.
             if (!OperatingSystem.IsWindows() || PlatformDetection.IsInContainer)
@@ -42,21 +27,41 @@ void RunWithExpectedCodePage(int expectedCodePage)
                 return;
             }
 
-            int inputEncoding = Interop.GetConsoleCP();
-            int outputEncoding = Interop.GetConsoleOutputCP();
-
-            try
+            RemoteExecutor.Invoke(static () =>
             {
-                Interop.SetConsoleCP(ConsoleEncoding);
-                Interop.SetConsoleOutputCP(ConsoleEncoding);
+                // Remote processes inherit the runner's console; allocate a private one before changing its code pages.
+                if (Interop.FreeConsole() == 0)
+                {
+                    throw new Win32Exception();
+                }
+                if (Interop.AllocConsole() == 0)
+                {
+                    throw new Win32Exception();
+                }
+                if (Interop.SetConsoleCP(ConsoleEncoding) == 0 || Interop.SetConsoleOutputCP(ConsoleEncoding) == 0)
+                {
+                    throw new Win32Exception();
+                }
 
-                RunWithExpectedCodePage(ConsoleEncoding);
-            }
-            finally
-            {
-                Interop.SetConsoleCP(inputEncoding);
-                Interop.SetConsoleOutputCP(outputEncoding);
-            }
+                using var tests = new ProcessStandardConsoleTests();
+                tests.RunWithExpectedCodePage(ConsoleEncoding);
+            }).Dispose();
+        }
+
+        private void RunWithExpectedCodePage(int expectedCodePage)
+        {
+            Process p = CreateProcessLong();
+            p.StartInfo.RedirectStandardInput = true;
+            p.StartInfo.RedirectStandardOutput = true;
+            p.StartInfo.RedirectStandardError = true;
+            p.Start();
+
+            Assert.Equal(expectedCodePage, p.StandardInput.Encoding.CodePage);
+            Assert.Equal(expectedCodePage, p.StandardOutput.CurrentEncoding.CodePage);
+            Assert.Equal(expectedCodePage, p.StandardError.CurrentEncoding.CodePage);
+
+            p.Kill();
+            Assert.True(p.WaitForExit(WaitInMS));
         }
 
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
 
@@ -235,35 +235,41 @@ public void EnvironmentVariableContainingNull_ThrowsArgumentException()
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         public void TestSetEnvironmentOnChildProcess()
         {
-            const string name = "b5a715d3-d74f-465d-abb7-2abe844750c9";
-            Environment.SetEnvironmentVariable(name, "parent-process-value");
-
-            Process p = CreateProcess(() =>
+            RemoteExecutor.Invoke(static () =>
             {
-                if (Environment.GetEnvironmentVariable(name) != "child-process-value")
-                    return 1;
+                using var tests = new ProcessStartInfoTests();
+                const string name = "b5a715d3-d74f-465d-abb7-2abe844750c9";
+                Environment.SetEnvironmentVariable(name, "parent-process-value");
 
-                return RemoteExecutor.SuccessExitCode;
-            });
-            p.StartInfo.Environment.Add(name, "child-process-value");
-            p.Start();
+                Process p = tests.CreateProcess(() =>
+                {
+                    if (Environment.GetEnvironmentVariable(name) != "child-process-value")
+                        return 1;
 
-            Assert.True(p.WaitForExit(WaitInMS));
-            Assert.Equal(RemoteExecutor.SuccessExitCode, p.ExitCode);
+                    return RemoteExecutor.SuccessExitCode;
+                });
+                p.StartInfo.Environment.Add(name, "child-process-value");
+                p.Start();
+
+                Assert.True(p.WaitForExit(WaitInMS));
+                Assert.Equal(RemoteExecutor.SuccessExitCode, p.ExitCode);
+            }).Dispose();
         }
 
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         public void TestEnvironmentOfChildProcess()
         {
-            const string ExtraEnvVar = "TestEnvironmentOfChildProcess_SpecialStuff";
-            Environment.SetEnvironmentVariable(ExtraEnvVar, "\x1234" + Environment.NewLine + "\x5678"); // ensure some Unicode characters and newlines are in the output
-            const string EmptyEnvVar = "TestEnvironmentOfChildProcess_Empty";
-            Environment.SetEnvironmentVariable(EmptyEnvVar, "");
-            try
+            RemoteExecutor.Invoke(static () =>
             {
+                using var tests = new ProcessStartInfoTests();
+                const string ExtraEnvVar = "TestEnvironmentOfChildProcess_SpecialStuff";
+                Environment.SetEnvironmentVariable(ExtraEnvVar, "\x1234" + Environment.NewLine + "\x5678"); // ensure some Unicode characters and newlines are in the output
+                const string EmptyEnvVar = "TestEnvironmentOfChildProcess_Empty";
+                Environment.SetEnvironmentVariable(EmptyEnvVar, "");
+
                 // Schedule a process to see what env vars it gets.  Have it write out those variables
                 // to its output stream so we can read them.
-                Process p = CreateProcess(() =>
+                Process p = tests.CreateProcess(() =>
                 {
                     Console.Write(string.Join(ItemSeparator, Environment.GetEnvironmentVariables().Cast<DictionaryEntry>().Select(e => Convert.ToBase64String(Encoding.UTF8.GetBytes(e.Key + "=" + e.Value)))));
                     return RemoteExecutor.SuccessExitCode;
@@ -294,22 +300,19 @@ public void TestEnvironmentOfChildProcess()
                         string.Join(", ", envEnv.Except(actualEnv)),
                         Environment.NewLine,
                         string.Join(", ", actualEnv.Except(envEnv))));
-            }
-            finally
-            {
-                Environment.SetEnvironmentVariable(ExtraEnvVar, null);
-                Environment.SetEnvironmentVariable(EmptyEnvVar, null);
-            }
+            }).Dispose();
         }
 
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         public void EnvironmentNullValue()
         {
-            const string NullEnvVar = "TestEnvironmentOfChildProcess_Null";
-            Environment.SetEnvironmentVariable(NullEnvVar, "");
-            try
+            RemoteExecutor.Invoke(static () =>
             {
-                Process p = CreateProcess(() =>
+                using var tests = new ProcessStartInfoTests();
+                const string NullEnvVar = "TestEnvironmentOfChildProcess_Null";
+                Environment.SetEnvironmentVariable(NullEnvVar, "");
+
+                Process p = tests.CreateProcess(() =>
                 {
                     // Verify that setting the value to null in StartInfo is going to remove the process environment.
                     Assert.Null(Environment.GetEnvironmentVariable(NullEnvVar));
@@ -319,11 +322,7 @@ public void EnvironmentNullValue()
                 Assert.Null(p.StartInfo.Environment[NullEnvVar]);
                 p.Start();
                 Assert.True(p.WaitForExit(WaitInMS));
-            }
-            finally
-            {
-                Environment.SetEnvironmentVariable(NullEnvVar, null);
-            }
+            }).Dispose();
         }
 
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
 
@@ -93,35 +93,27 @@ public void ProcessStart_UseShellExecute_OnUnix_ThrowsWhenNoOpenerOnPath()
             }, options).Dispose();
         }
 
-        [Fact]
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         [OuterLoop("Opens program")]
         [SkipOnPlatform(TestPlatforms.MacCatalyst, "In App Sandbox mode, the process doesn't have read access to the binary.")]
         [SkipOnPlatform(TestPlatforms.iOS | TestPlatforms.tvOS | TestPlatforms.Android | TestPlatforms.Browser, "Not supported on iOS/tvOS/Android/Browser.")]
         public void ProcessStart_DirectoryNameInCurDirectorySameAsFileNameInExecDirectory_Success()
         {
-            string fileToOpen = "dotnet";
-            string curDir = Environment.CurrentDirectory;
-            string dotnetFolder = Path.Combine(Path.GetTempPath(),"dotnet");
-            bool shouldDelete = !Directory.Exists(dotnetFolder);
-            try
+            Directory.CreateDirectory(Path.Combine(TestDirectory, "dotnet"));
+
+            RemoteExecutor.Invoke(StartDotnet, new RemoteInvokeOptions
             {
-                Directory.SetCurrentDirectory(Path.GetTempPath());
-                Directory.CreateDirectory(dotnetFolder);
+                StartInfo = new ProcessStartInfo { WorkingDirectory = TestDirectory }
+            }).Dispose();
 
+            static void StartDotnet()
+            {
+                string fileToOpen = "dotnet";
                 using (var px = Process.Start(fileToOpen))
                 {
                     Assert.NotNull(px);
                 }
             }
-            finally
-            {
-                if (shouldDelete)
-                {
-                    Directory.Delete(dotnetFolder);
-                }
-
-                Directory.SetCurrentDirectory(curDir);
-            }
         }
 
         [Fact]
 
@@ -123,6 +123,11 @@ private static unsafe void ReEnableCtrlCHandlerIfNeeded(PosixSignal signal)
 
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         public void Kill_EntireProcessTree_MinimalExceptions()
+        {
+            RemoteExecutor.Invoke(KillEntireProcessTreeMinimalExceptions).Dispose();
+        }
+
+        private static void KillEntireProcessTreeMinimalExceptions()
         {
             // This test validates that Kill(true) doesn't throw excessive exceptions internally
             // during process enumeration, which causes severe performance degradation with debugger attached.
 
@@ -10,6 +10,7 @@
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'windows'">$(DefineConstants);TargetsWindows</DefineConstants>
+    <DefineConstants Condition="'$(TargetOS)' == 'osx' and '$(TargetPlatformIdentifier)' == 'unix'">$(DefineConstants);TARGET_OSX</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(CommonPath)System\IO\StringParser.cs"