[browser][ST] test trimming of System.Collections.Concurrent

src/libraries/System.Runtime/tests/System.Runtime.Tests/TrimmingTests/BrowserDoesNotIncludeConcurrentTypes.cs

@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Linq;
+using System.Reflection;
+
+
+/// <summary>
+/// Tests that concurrent collections are not included in a trimmed app targeting browser.
+/// The idea is that the runtime should not depend on these types when running in a browser.
+/// Motivation: application size.
+/// Except ConcurrentDictionary which is used by other parts of the runtime and many apps.
+/// </summary>
+class Program
+{
+    static int Main(string[] args)
+    {
+        var bagType = GetTypeByName("ConcurrentBag`1");
+        if (bagType != null)
+        {
+            Console.WriteLine("Failed ConcurrentBag");
+            return -2;
+        }
+        var stackType = GetTypeByName("ConcurrentStack`1");
+        if (stackType != null)
+        {
+            Console.WriteLine("Failed ConcurrentStack");
+            return -3;
+        }
+        var collectionType = GetTypeByName("BlockingCollection`1");
+        if (collectionType != null)
+        {
+            Console.WriteLine("Failed BlockingCollection");
+            return -4;
+        }
+        var queueType = GetTypeByName("ConcurrentQueue`1");
+        if (queueType != null)
+        {
+            Console.WriteLine("Failed ConcurrentQueue");
+            return -5;
+        }
+        if (AppDomain.CurrentDomain.GetAssemblies().Any(a => a.GetName().Name == "System.Collections.Concurrent"))
+        {
+            Console.WriteLine("Failed: System.Collections.Concurrent assembly is present");
+            return -6;
+        }
+        return 100;
+    }
+
+    // make reflection trimmer incompatible
+    static Type GetTypeByName(string typeName)
+    {
+        foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
+        {
+            var type = assembly.GetType("System.Collections.Concurrent." + typeName);
+            if (type != null)
+            {
+                return type;
+            }
+        }
+        return null;
+    }
+}

src/libraries/System.Runtime/tests/System.Runtime.Tests/TrimmingTests/System.Runtime.TrimmingTests.proj

@@ -79,6 +79,9 @@
       <EnabledProperties>UseWindowsThreadPool</EnabledProperties>
     </TestConsoleAppSourceFiles>
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetsBrowser)' == 'true' and '$(WasmEnableThreads)' != 'true'">
+    <TestConsoleAppSourceFiles Include="BrowserDoesNotIncludeConcurrentTypes.cs" />
+  </ItemGroup>
 
   <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.targets))" />
 </Project>