diff --git a/scripts/build/TestPlatform.Dependencies.props b/scripts/build/TestPlatform.Dependencies.props
index 84df778cdc..fc53f36c50 100644
--- a/scripts/build/TestPlatform.Dependencies.props
+++ b/scripts/build/TestPlatform.Dependencies.props
@@ -28,6 +28,7 @@
     <NUnitConsoleRunnerVersion>3.8.0</NUnitConsoleRunnerVersion>
 
     <ChutzpahAdapterVersion>4.4.12</ChutzpahAdapterVersion>
+    <FluentAssertionsVersion>6.7.0</FluentAssertionsVersion>
 
     <!-- Versions that are used when building projects from TestAssets.sln for compatibility tests. See Invoke-TestAssetsBuild in scripts/build.ps1.
     Exact versions are used to avoid Nuget substituting them by closest match, if we make a typo.
diff --git a/scripts/build/TestPlatform.Settings.targets b/scripts/build/TestPlatform.Settings.targets
index 3e2ce6cb9e..4eca46ed75 100644
--- a/scripts/build/TestPlatform.Settings.targets
+++ b/scripts/build/TestPlatform.Settings.targets
@@ -116,21 +116,11 @@
           <FromP2P>true</FromP2P>
         </ProjectReference>
 
-        <PackageReference Include="MSTest.TestFramework">
-          <Version>$(MSTestFrameworkVersion)</Version>
-        </PackageReference>
-        <PackageReference Include="MSTest.TestAdapter">
-          <Version>$(MSTestAdapterVersion)</Version>
-        </PackageReference>
-        <PackageReference Include="Moq">
-          <Version>$(MoqVersion)</Version>
-        </PackageReference>
-        <PackageReference Include="MSTest.Assert.Extensions">
-          <Version>$(MSTestAssertExtensionVersion)</Version>
-        </PackageReference>
-        <PackageReference Include="Microsoft.CodeCoverage">
-          <Version>$(MicrosoftCodeCoverageVersion)</Version>
-        </PackageReference>
+        <PackageReference Include="MSTest.TestFramework" Version="$(MSTestFrameworkVersion)" />
+        <PackageReference Include="MSTest.TestAdapter" Version="$(MSTestAdapterVersion)" />
+        <PackageReference Include="MSTest.Assert.Extensions" Version="$(MSTestAssertExtensionVersion)" />
+        <PackageReference Include="Moq" Version="$(MoqVersion)" />
+        <PackageReference Include="Microsoft.CodeCoverage" Version="$(MicrosoftCodeCoverageVersion)" />
       </ItemGroup>
     </When>
   </Choose>
diff --git a/src/Microsoft.TestPlatform.ObjectModel/PublicAPI/PublicAPI.Shipped.txt b/src/Microsoft.TestPlatform.ObjectModel/PublicAPI/PublicAPI.Shipped.txt
index 5a67f67e54..3e4e800065 100644
--- a/src/Microsoft.TestPlatform.ObjectModel/PublicAPI/PublicAPI.Shipped.txt
+++ b/src/Microsoft.TestPlatform.ObjectModel/PublicAPI/PublicAPI.Shipped.txt
@@ -958,3 +958,6 @@ Microsoft.VisualStudio.TestPlatform.ObjectModel.Client.DiscoveryCompleteEventArg
 Microsoft.VisualStudio.TestPlatform.ObjectModel.Client.DiscoveryCompleteEventArgs.NotDiscoveredSources.get -> System.Collections.Generic.IList<string>
 Microsoft.VisualStudio.TestPlatform.ObjectModel.Client.DiscoveryCompleteEventArgs.PartiallyDiscoveredSources.get -> System.Collections.Generic.IList<string>
 Microsoft.VisualStudio.TestPlatform.ObjectModel.Client.DiscoveryCompleteEventArgs.SkippedDiscoveredSources.get -> System.Collections.Generic.IList<string>
+Microsoft.VisualStudio.TestPlatform.ObjectModel.RunConfiguration.DefaultPlatform.get -> Microsoft.VisualStudio.TestPlatform.ObjectModel.Architecture?
+Microsoft.VisualStudio.TestPlatform.ObjectModel.RunConfiguration.DefaultPlatform.set -> void
+Microsoft.VisualStudio.TestPlatform.ObjectModel.RunConfiguration.DefaultPlatformSet.get -> bool
diff --git a/src/Microsoft.TestPlatform.ObjectModel/RunSettings/RunConfiguration.cs b/src/Microsoft.TestPlatform.ObjectModel/RunSettings/RunConfiguration.cs
index 9124ba00ab..19b6279053 100644
--- a/src/Microsoft.TestPlatform.ObjectModel/RunSettings/RunConfiguration.cs
+++ b/src/Microsoft.TestPlatform.ObjectModel/RunSettings/RunConfiguration.cs
@@ -22,6 +22,8 @@ public class RunConfiguration : TestRunSettings
     /// </summary>
     private Architecture _platform;
 
+    private Architecture? _defaultPlatform;
+
     /// <summary>
     /// Maximum number of cores that the engine can use to run tests in parallel
     /// </summary>
@@ -234,7 +236,7 @@ public bool DisableParallelization
     }
 
     /// <summary>
-    /// Gets or sets the Target platform this run is targeting. Possible values are <c>x86|x64|arm|anycpu</c>.
+    /// Gets or sets the Target platform this run is targeting. Possible values are <see cref="Architecture"/> except for AnyCPU and Default.
     /// </summary>
     public Architecture TargetPlatform
     {
@@ -250,6 +252,23 @@ public Architecture TargetPlatform
         }
     }
 
+    /// <summary>
+    /// Gets or sets the default platform that will be used for AnyCPU sources, or non-dll sources. Possible values are <see cref="Architecture"/> except for AnyCPU and Default.
+    /// </summary>
+    public Architecture? DefaultPlatform
+    {
+        get
+        {
+            return _defaultPlatform;
+        }
+
+        set
+        {
+            _defaultPlatform = value;
+            DefaultPlatformSet = true;
+        }
+    }
+
     /// <summary>
     /// Gets or sets the target Framework this run is targeting.
     /// </summary>
@@ -348,6 +367,15 @@ public bool TargetPlatformSet
         private set;
     }
 
+    /// <summary>
+    /// Gets a value indicating whether default platform is set.
+    /// </summary>
+    public bool DefaultPlatformSet
+    {
+        get;
+        private set;
+    }
+
     /// <summary>
     /// Gets a value indicating whether maximum parallelization count is set.
     /// </summary>
@@ -455,6 +483,13 @@ public override XmlElement ToXml()
         targetPlatform.InnerXml = TargetPlatform.ToString();
         root.AppendChild(targetPlatform);
 
+        if (DefaultPlatform != null)
+        {
+            XmlElement defaultPlatform = doc.CreateElement("DefaultPlatform");
+            defaultPlatform.InnerXml = DefaultPlatform.ToString();
+            root.AppendChild(defaultPlatform);
+        }
+
         XmlElement maxCpuCount = doc.CreateElement("MaxCpuCount");
         maxCpuCount.InnerXml = MaxCpuCount.ToString();
         root.AppendChild(maxCpuCount);
@@ -737,6 +772,34 @@ public static RunConfiguration FromXml(XmlReader reader)
                         runConfiguration.TargetPlatform = archType;
                         break;
 
+                    case nameof(DefaultPlatform):
+                        XmlRunSettingsUtilities.ThrowOnHasAttributes(reader);
+                        Architecture defaultArchType;
+                        string defaultPlatformValue = reader.ReadElementContentAsString();
+                        try
+                        {
+                            defaultArchType = (Architecture)Enum.Parse(typeof(Architecture), defaultPlatformValue, true);
+                            // Ensure that the parsed value is actually in the enum, and that Default or AnyCpu are not provided.
+                            if (!Enum.IsDefined(typeof(Architecture), defaultArchType) || Architecture.Default == defaultArchType || Architecture.AnyCPU == defaultArchType)
+                            {
+                                throw new SettingsException(
+                                    string.Format(
+                                        CultureInfo.CurrentCulture,
+                                        Resources.Resources.InvalidSettingsIncorrectValue,
+                                        Constants.RunConfigurationSettingsName,
+                                        defaultPlatformValue,
+                                        elementName));
+                            }
+                        }
+                        catch (ArgumentException)
+                        {
+                            throw new SettingsException(string.Format(CultureInfo.CurrentCulture,
+                                Resources.Resources.InvalidSettingsIncorrectValue, Constants.RunConfigurationSettingsName, defaultPlatformValue, elementName));
+                        }
+
+                        runConfiguration.DefaultPlatform = defaultArchType;
+                        break;
+
                     case "TargetFrameworkVersion":
                         XmlRunSettingsUtilities.ThrowOnHasAttributes(reader);
                         Framework frameworkType;
diff --git a/src/vstest.console/TestPlatformHelpers/TestRequestManager.cs b/src/vstest.console/TestPlatformHelpers/TestRequestManager.cs
index a7cf09071d..bbb526abbc 100644
--- a/src/vstest.console/TestPlatformHelpers/TestRequestManager.cs
+++ b/src/vstest.console/TestPlatformHelpers/TestRequestManager.cs
@@ -813,15 +813,21 @@ Architecture GetDefaultArchitecture(RunConfiguration runConfiguration, string ru
                 return runConfiguration.TargetPlatform;
             }
 
+            Architecture? defaultArchitectureFromRunsettings = runConfiguration.DefaultPlatform;
+            if (defaultArchitectureFromRunsettings != null)
+            {
+                return defaultArchitectureFromRunsettings.Value;
+            }
+
             // Returns null, where there are none.
             Dictionary<string, string?>? environmentVariables = InferRunSettingsHelper.GetEnvironmentVariables(runsettingsXml);
             if (environmentVariables != null)
             {
-                string? defaultArchitectureFromRunsettings = environmentVariables.TryGetValue(VSTEST_DEFAULT_ARCHITECTURE_FOR_ANYCPU, out var architecture) ? architecture : null;
+                string? defaultArchitectureFromRunsettingsEnvironmentVariables = environmentVariables.TryGetValue(VSTEST_DEFAULT_ARCHITECTURE_FOR_ANYCPU, out var architecture) ? architecture : null;
 
-                if (defaultArchitectureFromRunsettings != null)
+                if (defaultArchitectureFromRunsettingsEnvironmentVariables != null)
                 {
-                    Architecture? defaultArchitecture = Enum.TryParse<Architecture>(defaultArchitectureFromRunsettings, out var arch) ? arch : null;
+                    Architecture? defaultArchitecture = Enum.TryParse<Architecture>(defaultArchitectureFromRunsettingsEnvironmentVariables, out var arch) ? arch : null;
 
                     if (defaultArchitecture != null)
                     {
diff --git a/test/Microsoft.TestPlatform.AcceptanceTests/Microsoft.TestPlatform.AcceptanceTests.csproj b/test/Microsoft.TestPlatform.AcceptanceTests/Microsoft.TestPlatform.AcceptanceTests.csproj
index 5262c3eba1..5910cccd71 100644
--- a/test/Microsoft.TestPlatform.AcceptanceTests/Microsoft.TestPlatform.AcceptanceTests.csproj
+++ b/test/Microsoft.TestPlatform.AcceptanceTests/Microsoft.TestPlatform.AcceptanceTests.csproj
@@ -29,7 +29,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Chutzpah" Version="$(ChutzpahAdapterVersion)" />
-    <PackageReference Include="FluentAssertions" Version="6.0.0-alpha0002" />
+    <PackageReference Include="FluentAssertions" Version="$(FluentAssertionsVersion)" />
     <PackageReference Include="Microsoft.TestPlatform.TestAsset.NativeCPP" Version="2.0.0" />
     <PackageReference Include="Microsoft.TestPlatform.QTools.Assets" Version="2.0.0" />
     <PackageReference Include="Procdump" Version="0.0.1" />
diff --git a/test/Microsoft.TestPlatform.CrossPlatEngine.UnitTests/Client/Parallel/ParallelOperationManagerTests.cs b/test/Microsoft.TestPlatform.CrossPlatEngine.UnitTests/Client/Parallel/ParallelOperationManagerTests.cs
index 392be647ad..c1b1982325 100644
--- a/test/Microsoft.TestPlatform.CrossPlatEngine.UnitTests/Client/Parallel/ParallelOperationManagerTests.cs
+++ b/test/Microsoft.TestPlatform.CrossPlatEngine.UnitTests/Client/Parallel/ParallelOperationManagerTests.cs
@@ -62,7 +62,7 @@ public void OperationManagerShouldRunOnlyMaximumParallelLevelOfWorkInParallelEve
         parallelOperationManager.StartWork(workloads, eventHandler, getEventHandler, runWorkload);
 
         // Assert
-        workerCounts.Should().BeEquivalentTo(3, 3, 3, 2, 1);
+        workerCounts.Should().BeEquivalentTo(new[] { 3, 3, 3, 2, 1 });
     }
 
     [TestMethod]
@@ -95,7 +95,7 @@ public void OperationManagerShouldCreateOnlyAsManyParallelWorkersAsThereAreWorkl
         parallelOperationManager.StartWork(workloads, eventHandler, getEventHandler, runWorkload);
 
         // Assert
-        workerCounts.Should().BeEquivalentTo(2, 1);
+        workerCounts.Should().BeEquivalentTo(new[] { 2, 1 });
     }
 
 
@@ -131,10 +131,10 @@ public void OperationManagerShouldCreateAsManyMaxParallelLevel()
         parallelOperationManager.StartWork(workloads, eventHandler, getEventHandler, runWorkload);
 
         // Assert
-        workerCounts.Should().BeEquivalentTo(2, 1);
+        workerCounts.Should().BeEquivalentTo(new[] { 2, 1 });
         // We create 10 slots, because that is the max parallel level, when we observe, there are 2 workloads running,
         // and then 1 workload running, so we see 8 and 9 (10 - 2, and 10 - 1).
-        availableWorkerCounts.Should().BeEquivalentTo(8, 9);
+        availableWorkerCounts.Should().BeEquivalentTo(new[] { 8, 9 });
     }
 
     [TestMethod]
@@ -177,7 +177,7 @@ public void OperationManagerMovesToTheNextWorkloadOnlyWhenRunNextWorkIsCalled()
         // even though we did not process workloads 4 and 5.
         // (e.g. In real life Abort was called so the handler won't call RunNextWork, because we don't want to run the remaining sources,
         // and all the sources that are currently running be aborted by calling Abort on each manager via DoActionOnAllManagers.)
-        workloadsProcessed.Should().BeEquivalentTo(1, 2, 3);
+        workloadsProcessed.Should().BeEquivalentTo(new[] { 1, 2, 3 });
     }
 
     [TestMethod]
@@ -231,7 +231,7 @@ public void OperationManagerRunsAnOperationOnAllActiveManagersWhenDoActionOnAllM
         // When we aborted workload 1 was already processed, and 2, and 3 were active.
         // We should see that the first manager did not call abort, but second and third called abort,
         // and there were no more managers created because we stopped calling next after 1 was done.
-        createdManagers.Select(manager => manager.AbortCalled).Should().BeEquivalentTo(false, true, true);
+        createdManagers.Select(manager => manager.AbortCalled).Should().BeEquivalentTo(new[] { false, true, true });
     }
 
     /// <summary>
diff --git a/test/Microsoft.TestPlatform.PerformanceTests/Microsoft.TestPlatform.PerformanceTests.csproj b/test/Microsoft.TestPlatform.PerformanceTests/Microsoft.TestPlatform.PerformanceTests.csproj
index cf33f901f3..af0562c9a4 100644
--- a/test/Microsoft.TestPlatform.PerformanceTests/Microsoft.TestPlatform.PerformanceTests.csproj
+++ b/test/Microsoft.TestPlatform.PerformanceTests/Microsoft.TestPlatform.PerformanceTests.csproj
@@ -13,7 +13,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.ApplicationInsights" Version="2.20.0" />
-    <PackageReference Include="FluentAssertions" Version="6.0.0-alpha0002" />
+    <PackageReference Include="FluentAssertions" Version="$(FluentAssertionsVersion)" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Microsoft.TestPlatform.TestUtilities\Microsoft.TestPlatform.TestUtilities.csproj" />
diff --git a/test/Microsoft.TestPlatform.TestUtilities/Microsoft.TestPlatform.TestUtilities.csproj b/test/Microsoft.TestPlatform.TestUtilities/Microsoft.TestPlatform.TestUtilities.csproj
index f64f1b11b6..056a13875c 100644
--- a/test/Microsoft.TestPlatform.TestUtilities/Microsoft.TestPlatform.TestUtilities.csproj
+++ b/test/Microsoft.TestPlatform.TestUtilities/Microsoft.TestPlatform.TestUtilities.csproj
@@ -26,7 +26,7 @@
     <ProjectReference Include="..\..\src\Microsoft.TestPlatform.VsTestConsole.TranslationLayer\Microsoft.TestPlatform.VsTestConsole.TranslationLayer.csproj" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="6.0.0-alpha0002" />
+    <PackageReference Include="FluentAssertions" Version="$(FluentAssertionsVersion)" />
     <PackageReference Include="Moq" Version="$(MoqVersion)" />
     <PackageReference Include="MSTest.TestFramework" Version="$(MSTestFrameworkVersion)" />
   </ItemGroup>
diff --git a/test/vstest.ProgrammerTests/vstest.ProgrammerTests.csproj b/test/vstest.ProgrammerTests/vstest.ProgrammerTests.csproj
index 435b57d4fd..6c214a10d1 100644
--- a/test/vstest.ProgrammerTests/vstest.ProgrammerTests.csproj
+++ b/test/vstest.ProgrammerTests/vstest.ProgrammerTests.csproj
@@ -16,7 +16,7 @@
     <OutputType>Exe</OutputType>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="6.0.0-alpha0002" />
+    <PackageReference Include="FluentAssertions" Version="$(FluentAssertionsVersion)" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\src\Microsoft.TestPlatform.CoreUtilities\Microsoft.TestPlatform.CoreUtilities.csproj" />
diff --git a/test/vstest.console.UnitTests/TestPlatformHelpers/TestRequestManagerTests.cs b/test/vstest.console.UnitTests/TestPlatformHelpers/TestRequestManagerTests.cs
index 750392c7f1..9c08bef69b 100644
--- a/test/vstest.console.UnitTests/TestPlatformHelpers/TestRequestManagerTests.cs
+++ b/test/vstest.console.UnitTests/TestPlatformHelpers/TestRequestManagerTests.cs
@@ -9,6 +9,8 @@
 using System.Threading;
 using System.Threading.Tasks;
 
+using FluentAssertions;
+
 using Microsoft.VisualStudio.TestPlatform.Client.RequestHelper;
 using Microsoft.VisualStudio.TestPlatform.CommandLine;
 using Microsoft.VisualStudio.TestPlatform.CommandLine.Processors;
@@ -2571,4 +2573,72 @@ private void DiscoverTestsIfThrowsExceptionShouldThrowOut(Exception exception)
 
         _testRequestManager.DiscoverTests(payload, mockDiscoveryEventsRegistrar.Object, _protocolConfig);
     }
+
+    [TestMethod]
+    [DataRow("x86")]
+    [DataRow("x64")]
+    [DataRow("arm64")]
+    public void SettingDefaultPlatformUsesItForAnyCPUSourceButNotForNonAnyCPUSource(string defaultPlatform)
+    {
+        // -- Arrange
+        var payload = new DiscoveryRequestPayload()
+        {
+            Sources = new List<string>() { "AnyCPU.dll", "x64.dll" },
+            RunSettings =
+                $@"<?xml version=""1.0"" encoding=""utf-8""?>
+                <RunSettings>
+                     <RunConfiguration>
+                       <DefaultPlatform>{defaultPlatform}</DefaultPlatform>
+                     </RunConfiguration>
+                </RunSettings>"
+        };
+
+        Architecture expectedPlatform = (Architecture)Enum.Parse(typeof(Architecture), defaultPlatform, ignoreCase: true);
+
+        Dictionary<string, SourceDetail>? actualSourceToSourceDetailMap = null;
+        var mockDiscoveryRequest = new Mock<IDiscoveryRequest>();
+
+        _mockAssemblyMetadataProvider.Setup(m => m.GetArchitecture("AnyCPU.dll")).Returns(Architecture.AnyCPU);
+        _mockAssemblyMetadataProvider.Setup(m => m.GetArchitecture("x64.dll")).Returns(Architecture.X64);
+
+        _mockTestPlatform.Setup(mt => mt.CreateDiscoveryRequest(It.IsAny<IRequestData>(), It.IsAny<DiscoveryCriteria>(), It.IsAny<TestPlatformOptions>(), It.IsAny<Dictionary<string, SourceDetail>>(), It.IsAny<IWarningLogger>()))
+            .Callback((IRequestData _, DiscoveryCriteria _, TestPlatformOptions _, Dictionary<string, SourceDetail> sourceToSourceDetailMap, IWarningLogger _) =>
+                // output the incoming sourceToSourceDetailMap to the variable above so we can inspect it.
+                actualSourceToSourceDetailMap = sourceToSourceDetailMap
+            ).Returns(mockDiscoveryRequest.Object);
+
+        // -- Act
+        // The substitution of architecture happens in runsettings patching which is shared for discovery and run
+        // so we can safely just test discovery.
+        _testRequestManager.DiscoverTests(payload, new Mock<ITestDiscoveryEventsRegistrar>().Object, _protocolConfig);
+
+        actualSourceToSourceDetailMap.Should().NotBeNull();
+        // The AnyCPU dll is the architecture we provide in the default setting, rather than being determined from the
+        // current process architecture.
+        actualSourceToSourceDetailMap!["AnyCPU.dll"].Architecture.Should().Be(expectedPlatform);
+        // The dll that has a specific architecture always remains that specific architecture.
+        actualSourceToSourceDetailMap!["x64.dll"].Architecture.Should().Be(Architecture.X64);
+    }
+
+    [TestMethod]
+    public void UsingInvalidValueForDefaultPlatformSettingThrowsSettingsException()
+    {
+        var settingXml = @"
+            <RunSettings>
+                <RunConfiguration>
+                    <DefaultPlatform>WRONGPlatform</DefaultPlatform>
+                </RunConfiguration>
+            </RunSettings>";
+
+        var payload = new TestRunRequestPayload()
+        {
+            Sources = new List<string>() { "a.dll" },
+            RunSettings = settingXml
+        };
+
+        _testRequestManager
+            .Invoking(m => m.RunTests(payload, new Mock<ITestHostLauncher3>().Object, new Mock<ITestRunEventsRegistrar>().Object, _protocolConfig))
+            .Should().Throw<SettingsException>()
+            .And.Message.Should().Contain("Invalid value 'WRONGPlatform' specified for 'DefaultPlatform'.");
+    }
 }
diff --git a/test/vstest.console.UnitTests/vstest.console.UnitTests.csproj b/test/vstest.console.UnitTests/vstest.console.UnitTests.csproj
index d0b644826b..acfc1c9f7d 100644
--- a/test/vstest.console.UnitTests/vstest.console.UnitTests.csproj
+++ b/test/vstest.console.UnitTests/vstest.console.UnitTests.csproj
@@ -22,6 +22,9 @@
       <FromP2P>true</FromP2P>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="FluentAssertions" Version="$(FluentAssertionsVersion)" />
+  </ItemGroup>
   <ItemGroup Condition=" '$(TargetFramework)' == 'net48' ">
     <Reference Include="System.Runtime" />
     <Reference Include="System" />