fix assembly dependencies resolver for netcore

src/NUnitEngine/nunit.engine.core/Internal/TestAssemblyLoadContext.cs

@@ -15,31 +15,57 @@ internal sealed class TestAssemblyLoadContext : AssemblyLoadContext
         private readonly string _testAssemblyPath;
         private readonly string _basePath;
         private readonly TestAssemblyResolver _resolver;
+        private readonly System.Runtime.Loader.AssemblyDependencyResolver _runtimeResolver;
 
         public TestAssemblyLoadContext(string testAssemblyPath)
         {
             _testAssemblyPath = testAssemblyPath;
             _resolver = new TestAssemblyResolver(this, testAssemblyPath);
             _basePath = Path.GetDirectoryName(testAssemblyPath);
+            _runtimeResolver = new AssemblyDependencyResolver(testAssemblyPath);
         }
 
         protected override Assembly Load(AssemblyName name)
         {
             var assemblies = AppDomain.CurrentDomain.GetAssemblies();
             var loadedAssembly = assemblies.FirstOrDefault(x => x.GetName().Name == name.Name);
+            if (loadedAssembly != null)
+            {
+                return loadedAssembly;
+            }
+
+            loadedAssembly = base.Load(name);
+            if (loadedAssembly != null)
+            {
+                return loadedAssembly;
+            }
+
+            var runtimeResolverPath = _runtimeResolver.ResolveAssemblyToPath(name);
+            if (string.IsNullOrEmpty(runtimeResolverPath) == false &&
+                File.Exists(runtimeResolverPath))
+            {
+                loadedAssembly = LoadFromAssemblyPath(runtimeResolverPath);
+            }
+
+            if (loadedAssembly != null)
+            {
+                return loadedAssembly;
+            }
 
+            loadedAssembly = _resolver.Resolve(this, name);
             if (loadedAssembly != null)
-                loadedAssembly = base.Load(name);
+            {
+                return loadedAssembly;
+            }
 
-            if (loadedAssembly == null)
+            // Load assemblies that are dependencies, and in the same folder as the test assembly,
+            // but are not fully specified in test assembly deps.json file. This happens when the
+            // dependencies reference in the csproj file has CopyLocal=false, and for example, the
+            // reference is a projectReference and has the same output directory as the parent.
+            string assemblyPath = Path.Combine(_basePath, name.Name + ".dll");
+            if (File.Exists(assemblyPath))
             {
-                // Load assemblies that are dependencies, and in the same folder as the test assembly,
-                // but are not fully specified in test assembly deps.json file. This happens when the
-                // dependencies reference in the csproj file has CopyLocal=false, and for example, the
-                // reference is a projectReference and has the same output directory as the parent.
-                string assemblyPath = Path.Combine(_basePath, name.Name + ".dll");
-                if (File.Exists(assemblyPath))
-                    loadedAssembly = LoadFromAssemblyPath(assemblyPath);
+                loadedAssembly = LoadFromAssemblyPath(assemblyPath);
             }
 
             return loadedAssembly;

src/NUnitEngine/nunit.engine.core/Internal/TestAssemblyResolver.cs

@@ -55,6 +55,11 @@ public void Dispose()
             _loadContext.Resolving -= OnResolving;
         }
 
+        public Assembly Resolve(AssemblyLoadContext context, AssemblyName name)
+        {
+            return OnResolving(context, name);
+        }
+
         private Assembly OnResolving(AssemblyLoadContext context, AssemblyName name)
         {
             foreach (var library in _dependencyContext.RuntimeLibraries)