diff --git a/src/libraries/Common/tests/TestUtilities/System/IO/FileCleanupTestBase.cs b/src/libraries/Common/tests/TestUtilities/System/IO/FileCleanupTestBase.cs
index c0bf23fe91d618..cce2ce07575f11 100644
--- a/src/libraries/Common/tests/TestUtilities/System/IO/FileCleanupTestBase.cs
+++ b/src/libraries/Common/tests/TestUtilities/System/IO/FileCleanupTestBase.cs
@@ -84,11 +84,12 @@ protected virtual void Dispose(bool disposing)
         protected string GetRandomLinkName() => GetTestFileName() + ".link";
         protected string GetRandomDirName()  => GetTestFileName() + "_dir";
 
-        protected string GetRandomFilePath() => Path.Combine(ActualTestDirectory.Value, GetRandomFileName());
-        protected string GetRandomLinkPath() => Path.Combine(ActualTestDirectory.Value, GetRandomLinkName());
-        protected string GetRandomDirPath()  => Path.Combine(ActualTestDirectory.Value, GetRandomDirName());
+        protected string GetRandomFilePath() => Path.Combine(TestDirectoryActualCasing, GetRandomFileName());
+        protected string GetRandomLinkPath() => Path.Combine(TestDirectoryActualCasing, GetRandomLinkName());
+        protected string GetRandomDirPath()  => Path.Combine(TestDirectoryActualCasing, GetRandomDirName());
 
-        private Lazy<string> ActualTestDirectory => new Lazy<string>(() => GetTestDirectoryActualCasing());
+        private string _testDirectoryActualCasing;
+        private string TestDirectoryActualCasing => _testDirectoryActualCasing ??= GetTestDirectoryActualCasing();
 
         /// <summary>Gets a test file full path that is associated with the call site.</summary>
         /// <param name="index">An optional index value to use as a suffix on the file name.  Typically a loop index.</param>
diff --git a/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs b/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
index f92ec2a8c0bb2d..67618c72842878 100644
--- a/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
+++ b/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
@@ -23,7 +23,7 @@ public static partial class PlatformDetection
         // do it in a way that failures don't cascade.
         //
 
-        private static Lazy<bool> s_IsInHelix => new Lazy<bool>(() => Environment.GetEnvironmentVariables().Keys.Cast<string>().Any(key => key.StartsWith("HELIX")));
+        private static readonly Lazy<bool> s_IsInHelix = new Lazy<bool>(() => Environment.GetEnvironmentVariables().Keys.Cast<string>().Any(key => key.StartsWith("HELIX")));
         public static bool IsInHelix => s_IsInHelix.Value;
 
         public static bool IsNetCore => Environment.Version.Major >= 5 || RuntimeInformation.FrameworkDescription.StartsWith(".NET Core", StringComparison.OrdinalIgnoreCase);
@@ -66,9 +66,9 @@ public static partial class PlatformDetection
         public static bool Is64BitProcess => IntPtr.Size == 8;
         public static bool IsNotWindows => !IsWindows;
 
-        private static Lazy<bool> s_isCheckedRuntime => new Lazy<bool>(() => AssemblyConfigurationEquals("Checked"));
-        private static Lazy<bool> s_isReleaseRuntime => new Lazy<bool>(() => AssemblyConfigurationEquals("Release"));
-        private static Lazy<bool> s_isDebugRuntime => new Lazy<bool>(() => AssemblyConfigurationEquals("Debug"));
+        private static readonly Lazy<bool> s_isCheckedRuntime = new Lazy<bool>(() => AssemblyConfigurationEquals("Checked"));
+        private static readonly Lazy<bool> s_isReleaseRuntime = new Lazy<bool>(() => AssemblyConfigurationEquals("Release"));
+        private static readonly Lazy<bool> s_isDebugRuntime = new Lazy<bool>(() => AssemblyConfigurationEquals("Debug"));
 
         public static bool IsCheckedRuntime => s_isCheckedRuntime.Value;
         public static bool IsReleaseRuntime => s_isReleaseRuntime.Value;
@@ -209,7 +209,7 @@ public static bool IsMetadataTokenSupported
         // Linux - OpenSsl supports alpn from openssl 1.0.2 and higher.
         // OSX - SecureTransport doesn't expose alpn APIs. TODO https://github.com/dotnet/runtime/issues/27727
         // Android - Platform supports alpn from API level 29 and higher
-        private static Lazy<bool> s_supportsAlpn = new Lazy<bool>(GetAlpnSupport);
+        private static readonly Lazy<bool> s_supportsAlpn = new Lazy<bool>(GetAlpnSupport);
         private static bool GetAlpnSupport()
         {
             if (IsWindows && !IsWindows7 && !IsNetFramework)
@@ -238,11 +238,11 @@ private static bool GetAlpnSupport()
         public static bool SupportsAlpn => s_supportsAlpn.Value;
         public static bool SupportsClientAlpn => SupportsAlpn || IsOSX || IsMacCatalyst || IsiOS || IstvOS;
 
-        private static Lazy<bool> s_supportsTls10 = new Lazy<bool>(GetTls10Support);
-        private static Lazy<bool> s_supportsTls11 = new Lazy<bool>(GetTls11Support);
-        private static Lazy<bool> s_supportsTls12 = new Lazy<bool>(GetTls12Support);
-        private static Lazy<bool> s_supportsTls13 = new Lazy<bool>(GetTls13Support);
-        private static Lazy<bool> s_sendsCAListByDefault = new Lazy<bool>(GetSendsCAListByDefault);
+        private static readonly Lazy<bool> s_supportsTls10 = new Lazy<bool>(GetTls10Support);
+        private static readonly Lazy<bool> s_supportsTls11 = new Lazy<bool>(GetTls11Support);
+        private static readonly Lazy<bool> s_supportsTls12 = new Lazy<bool>(GetTls12Support);
+        private static readonly Lazy<bool> s_supportsTls13 = new Lazy<bool>(GetTls13Support);
+        private static readonly Lazy<bool> s_sendsCAListByDefault = new Lazy<bool>(GetSendsCAListByDefault);
 
         public static bool SupportsTls10 => s_supportsTls10.Value;
         public static bool SupportsTls11 => s_supportsTls11.Value;
@@ -251,7 +251,7 @@ private static bool GetAlpnSupport()
         public static bool SendsCAListByDefault => s_sendsCAListByDefault.Value;
         public static bool SupportsSendingCustomCANamesInTls => UsesAppleCrypto || IsOpenSslSupported || (PlatformDetection.IsWindows8xOrLater && SendsCAListByDefault);
 
-        private static Lazy<bool> s_largeArrayIsNotSupported = new Lazy<bool>(IsLargeArrayNotSupported);
+        private static readonly Lazy<bool> s_largeArrayIsNotSupported = new Lazy<bool>(IsLargeArrayNotSupported);
 
         [MethodImpl(MethodImplOptions.NoOptimization)]
         private static bool IsLargeArrayNotSupported()