diff --git a/src/DynamoUtilities/DynamoFeatureFlagsManager.cs b/src/DynamoUtilities/DynamoFeatureFlagsManager.cs
index 32be9566ca6..bc041138f35 100644
--- a/src/DynamoUtilities/DynamoFeatureFlagsManager.cs
+++ b/src/DynamoUtilities/DynamoFeatureFlagsManager.cs
@@ -2,16 +2,17 @@
 using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
-using System.ComponentModel;
 using System.Diagnostics;
 using System.IO;
-using System.Reflection;
 using System.Threading;
-using System.Threading.Tasks;
 
 namespace DynamoUtilities
 {
 
+    internal interface IFFlags
+    {
+        internal T CheckFeatureFlag<T>(DynamoFeatureFlagsManager mgr, string featureFlagKey, T defaultval);
+    }
 
     /// <summary>
     /// A wrapper around the DynamoFeatureFlags CLI tool.
@@ -20,9 +21,21 @@ namespace DynamoUtilities
     /// </summary>
     internal class DynamoFeatureFlagsManager : CLIWrapper
     {
+        // Utility class that supports mocking during tests
+        class FFlags : IFFlags
+        {
+            T IFFlags.CheckFeatureFlag<T>(DynamoFeatureFlagsManager mgr, string featureFlagKey, T defaultval)
+            {
+                return mgr.CheckFeatureFlagInternal(featureFlagKey, defaultval);
+            }
+        }
+
+        // Useful for mocking in tests
+        internal IFFlags flags { get; set; } = new FFlags();
         private string relativePath = Path.Combine("DynamoFeatureFlags", "DynamoFeatureFlags.exe");
         private Dictionary<string, object> AllFlagsCache { get; set; }//TODO lock is likely overkill.
         private SynchronizationContext syncContext;
+        private readonly bool testmode = false;
         internal static event Action FlagsRetrieved;
         
         //TODO(DYN-6464)- remove this field!.
@@ -43,8 +56,10 @@ internal class DynamoFeatureFlagsManager : CLIWrapper
         /// <param name="syncContext">context used for raising FlagRetrieved event.</param>
         /// <param name="testmode">will not contact feature flag service in testmode, will respond with defaults.</param>
         internal DynamoFeatureFlagsManager(string userkey, SynchronizationContext syncContext, bool testmode=false)
-        {  
+        {
             this.syncContext = syncContext;
+            this.testmode = testmode;
+
             //dont pass userkey arg if null/empty
             var userkeyarg = $"-u {userkey}";
             var testmodearg = string.Empty;
@@ -62,7 +77,6 @@ internal DynamoFeatureFlagsManager(string userkey, SynchronizationContext syncCo
 
         internal void CacheAllFlags()
         {
-
             //wait for response
             var dataFromCLI = GetData(featureFlagTimeoutMs);    
             //convert from json string to dictionary.
@@ -91,6 +105,13 @@ internal void CacheAllFlags()
         /// <param name="defaultval">Currently the flag and default val MUST be a bool or string.</param>
         /// <returns></returns>
         internal T CheckFeatureFlag<T>(string featureFlagKey, T defaultval)
+        {
+            // with testmode = true, the call goes through an interface so that we can intercept it with Mock
+            // with testmode = false, the call simply goes to the CheckFeatureFlagInternal
+            return testmode ? flags.CheckFeatureFlag(this, featureFlagKey, defaultval) : CheckFeatureFlagInternal(featureFlagKey, defaultval);
+        }
+
+        private T CheckFeatureFlagInternal<T>(string featureFlagKey, T defaultval)
         {
             if(!(defaultval is bool || defaultval is string)){
                 throw new ArgumentException("unsupported flag type", defaultval.GetType().ToString());
diff --git a/src/DynamoUtilities/Properties/AssemblyInfo.cs b/src/DynamoUtilities/Properties/AssemblyInfo.cs
index c4f51c14e99..6ff91d38d74 100644
--- a/src/DynamoUtilities/Properties/AssemblyInfo.cs
+++ b/src/DynamoUtilities/Properties/AssemblyInfo.cs
@@ -30,3 +30,5 @@
 [assembly: InternalsVisibleTo("Notifications")]
 [assembly: InternalsVisibleTo("SystemTestServices")]
 [assembly: InternalsVisibleTo("PackageManagerTests")]
+//DynamicProxyGenAssembly2 is used by Mock to allow stubbing internal interfaces
+[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")]
diff --git a/src/Tools/DynamoFeatureFlags/FeatureFlagsClient.cs b/src/Tools/DynamoFeatureFlags/FeatureFlagsClient.cs
index 8eaeb1b4bb8..26917652f79 100644
--- a/src/Tools/DynamoFeatureFlags/FeatureFlagsClient.cs
+++ b/src/Tools/DynamoFeatureFlags/FeatureFlagsClient.cs
@@ -85,9 +85,7 @@ internal FeatureFlagsClient(string userkey, string mobileKey = null, bool testMo
                 AllFlags = LdValue.ObjectFrom(new Dictionary<string,LdValue> { { "TestFlag1",LdValue.Of(true) },
                     { "TestFlag2", LdValue.Of("I am a string") },
                     //in tests we want instancing on so we can test it.
-                    { "graphics-primitive-instancing", LdValue.Of(true) },
-                    { "IsolatePackages", LdValue.Of("Package1,Package2,Package") },
-                    { "DoNotIsolatePackages", LdValue.Of("Package") }
+                    { "graphics-primitive-instancing", LdValue.Of(true) }
                 });
                 return;
             }
diff --git a/test/Libraries/PackageManagerTests/PackageLoaderTests.cs b/test/Libraries/PackageManagerTests/PackageLoaderTests.cs
index f52c2b90762..93400322194 100644
--- a/test/Libraries/PackageManagerTests/PackageLoaderTests.cs
+++ b/test/Libraries/PackageManagerTests/PackageLoaderTests.cs
@@ -652,13 +652,21 @@ public void PlacingCustomNodeInstanceFromPackageRetainsCorrectPackageInfoState()
         [Test]
         public void LoadPackagesInAssemblyIsolation()
         {
+            var ff = new Mock<DynamoUtilities.IFFlags>();
+            DynamoModel.FeatureFlags.flags = ff.Object;
+            ff.Setup(x => x.CheckFeatureFlag<string>(DynamoModel.FeatureFlags, "IsolatePackages", "")).Returns(() => "Package1,Package2,Package");
+            ff.Setup(x => x.CheckFeatureFlag<string>(DynamoModel.FeatureFlags, "DoNotIsolatePackages", "")).Returns(() => "Package");
+
             // Needed for FeatureFlags
             Assert.IsTrue(DynamoModel.IsTestMode);
             Assert.AreEqual("Package1,Package2,Package", DynamoModel.FeatureFlags.CheckFeatureFlag<string>("IsolatePackages", ""));
             Assert.AreEqual("Package", DynamoModel.FeatureFlags.CheckFeatureFlag<string>("DoNotIsolatePackages", ""));
-            
 
-            var loader = GetPackageLoader();
+            var pathManager = new Mock<Dynamo.Interfaces.IPathManager>();
+            pathManager.SetupGet(x => x.PackagesDirectories).Returns(
+                () => new List<string> { PackagesDirectory });
+
+            var loader = new PackageLoader(pathManager.Object);
             var libraryLoader = new ExtensionLibraryLoader(CurrentDynamoModel);
 
             loader.PackagesLoaded += libraryLoader.LoadPackages;