Make the build work with the .NET backend again.

With the latest HL2 payload, a few changes got in that broke the .NET backend (a combination of usage of C# language features that don't work with the .NET backend, or weird interactions with the test assembly setup)

Author: wiwei

Assets/MixedRealityToolkit.Examples/Demos/Gltf/Scripts/TestGlbLoading.cs

@@ -19,7 +19,7 @@ public class TestGlbLoading : MonoBehaviour
 
         private async void Start()
         {
-            Response response = default;
+            Response response = new Response();
 
             try
             {

Assets/MixedRealityToolkit.Services/InputSystem/FocusProvider.cs

@@ -798,7 +798,7 @@ private static void QueryScene(PointerData pointerData, LayerMask[] prioritizedL
                     case SceneQueryType.SimpleRaycast:
                         if (MixedRealityRaycaster.RaycastSimplePhysicsStep(pointerRays[i], prioritizedLayerMasks, out physicsHit))
                         {
-                            UpdatePointerRayOnHit(pointerData, pointerRays, in physicsHit, i, rayStartDistance);
+                            UpdatePointerRayOnHit(pointerData, pointerRays, physicsHit, i, rayStartDistance);
                             return;
                         }
                         break;
@@ -808,7 +808,7 @@ private static void QueryScene(PointerData pointerData, LayerMask[] prioritizedL
                     case SceneQueryType.SphereCast:
                         if (MixedRealityRaycaster.RaycastSpherePhysicsStep(pointerRays[i], pointerData.Pointer.SphereCastRadius, prioritizedLayerMasks, out physicsHit))
                         {
-                            UpdatePointerRayOnHit(pointerData, pointerRays, in physicsHit, i, rayStartDistance);
+                            UpdatePointerRayOnHit(pointerData, pointerRays, physicsHit, i, rayStartDistance);
                             return;
                         }
                         break;
@@ -854,7 +854,7 @@ private static void QueryScene(PointerData pointerData, LayerMask[] prioritizedL
             }
         }
 
-        private static void UpdatePointerRayOnHit(PointerData pointerData, RayStep[] raySteps, in RaycastHit physicsHit, int hitRayIndex, float rayStartDistance)
+        private static void UpdatePointerRayOnHit(PointerData pointerData, RayStep[] raySteps, RaycastHit physicsHit, int hitRayIndex, float rayStartDistance)
         {
             Vector3 origin = raySteps[hitRayIndex].Origin;
             Vector3 terminus = physicsHit.point;

Assets/MixedRealityToolkit.Tests/PlayModeTests/TestFixture_01_SimplePlayModeTest.cs

@@ -1,11 +1,17 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-using NUnit.Framework;
 using UnityEngine;
-using UnityEngine.TestTools;
 using System.Collections;
 
+#if !WINDOWS_UWP
+// When the .NET scripting backend is enabled and C# projects are built
+// Unity doesn't include the the required assemblies (i.e. the ones below).
+// Given that the .NET backend is deprecated by Unity at this point it's we have
+// to work around this on our end.
+using NUnit.Framework;
+using UnityEngine.TestTools;
+
 namespace Microsoft.MixedReality.Toolkit.Tests
 {
     public class TestFixture_01_SimplePlayModeTest
@@ -47,10 +53,6 @@ public IEnumerator Test01_WhizzySphere()
             }
             stopwatch.Stop();
         }
-
-        [TearDown]
-        public void TearDown()
-        {
-        }
     }
-}
+}
+#endif

Assets/MixedRealityToolkit.Tests/TestUtilities.cs

@@ -1,18 +1,22 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-using Microsoft.MixedReality.Toolkit.Editor;
-using NUnit.Framework;
 using System.Collections;
 using System.Linq;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 #if UNITY_EDITOR
+using Microsoft.MixedReality.Toolkit.Editor;
+using NUnit.Framework;
 using UnityEditor;
 using UnityEditor.SceneManagement;
 #endif
 
+#if WINDOWS_UWP
+using UnityEngine.Assertions;
+#endif
+
 namespace Microsoft.MixedReality.Toolkit.Tests
 {
     public static class TestUtilities
@@ -76,9 +80,13 @@ public static void InitializeMixedRealityToolkitScene(bool useDefaultProfile = f
             }
         }
 
-        public static T GetDefaultMixedRealityProfile<T>() where T : BaseMixedRealityProfile
+        private static T GetDefaultMixedRealityProfile<T>() where T : BaseMixedRealityProfile
         {
+#if UNITY_EDITOR
             return ScriptableObjectExtensions.GetAllInstances<T>().FirstOrDefault(profile => profile.name.Equals($"Default{typeof(T).Name}"));
+#else
+            return ScriptableObject.CreateInstance<T>();
+#endif
         }
     }
 }