diff --git a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignatureUtilityTests.cs b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignatureUtilityTests.cs
index f4b766c9eef..93b0c6e2966 100644
--- a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignatureUtilityTests.cs
+++ b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignatureUtilityTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 
 using System;
 using System.Collections.Generic;
diff --git a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignedPackageArchiveTests.cs b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignedPackageArchiveTests.cs
index d3c269140f0..d53820d567b 100644
--- a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignedPackageArchiveTests.cs
+++ b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SignedPackageArchiveTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System;
 using System.IO;
 using System.Security.Cryptography.X509Certificates;
diff --git a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SigningUtilityTests.cs b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SigningUtilityTests.cs
index f01d2671592..d9f884a1b78 100644
--- a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SigningUtilityTests.cs
+++ b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/SigningUtilityTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 
 using System;
 using System.Diagnostics;
diff --git a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/TimestampProviderTests.cs b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/TimestampProviderTests.cs
index e7fc94c91b9..e7d8e6a49ed 100644
--- a/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/TimestampProviderTests.cs
+++ b/test/NuGet.Core.FuncTests/NuGet.Packaging.FuncTest/SigningTests/TimestampProviderTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 
 using System;
 using System.Collections.Generic;
@@ -24,7 +24,6 @@ namespace NuGet.Packaging.FuncTest
     [Collection(SigningTestCollection.Name)]
     public class TimestampProviderTests
     {
-        private const string ArgumentNullExceptionMessage = "Value cannot be null.\r\nParameter name: {0}";
         private const string OperationCancelledExceptionMessage = "The operation was canceled.";
 
         private SigningTestFixture _testFixture;
@@ -70,7 +69,7 @@ public async Task GetTimestampAsync_WithValidInput_ReturnsTimestampAsync()
         }
 
         [CIOnlyFact]
-        public async Task GetTimestamp_AssertCompleteChain_SuccessAsync()
+        public async Task GetTimestampAsync_AssertCompleteChain_SuccessAsync()
         {
             var timestampService = await _testFixture.GetDefaultTrustedTimestampServiceAsync();
             var timestampProvider = new Rfc3161TimestampProvider(timestampService.Url);
@@ -157,12 +156,12 @@ public async Task GetTimestampAsync_WhenRequestNull_ThrowsAsync()
                     target: SignaturePlacement.PrimarySignature
                 );
 
-                // Act
-                Action timestampAction = async () => await timestampProvider.GetTimestampAsync(null, logger, CancellationToken.None);
-
                 // Assert
-                timestampAction.ShouldThrow<ArgumentNullException>()
-                    .WithMessage(string.Format(ArgumentNullExceptionMessage, nameof(request)));
+                var exception = await Assert.ThrowsAsync<ArgumentNullException>(
+                    () => timestampProvider.GetTimestampAsync(request: null, logger, CancellationToken.None));
+
+                Assert.Equal("request", exception.ParamName);
+                Assert.StartsWith("Value cannot be null.", exception.Message);
             }
         }
 
@@ -188,12 +187,12 @@ public async Task GetTimestampAsync_WhenLoggerNull_ThrowsAsync()
                     target: SignaturePlacement.PrimarySignature
                 );
 
-                // Act
-                Action timestampAction = async () => await timestampProvider.GetTimestampAsync(request, null, CancellationToken.None);
-
                 // Assert
-                timestampAction.ShouldThrow<ArgumentNullException>()
-                    .WithMessage(string.Format(ArgumentNullExceptionMessage, "logger"));
+                var exception = await Assert.ThrowsAsync<ArgumentNullException>(
+                    () => timestampProvider.GetTimestampAsync(request, logger: null, CancellationToken.None));
+
+                Assert.Equal("logger", exception.ParamName);
+                Assert.StartsWith("Value cannot be null.", exception.Message);
             }
         }
 
@@ -220,12 +219,11 @@ public async Task GetTimestampAsync_WhenCancelled_ThrowsAsync()
                    target: SignaturePlacement.PrimarySignature
                );
 
-                // Act
-                Action timestampAction = async () => await timestampProvider.GetTimestampAsync(request, logger, new CancellationToken(canceled: true));
-
                 // Assert
-                timestampAction.ShouldThrow<OperationCanceledException>()
-                    .WithMessage(OperationCancelledExceptionMessage);
+                var exception = await Assert.ThrowsAsync<OperationCanceledException>(
+                    () => timestampProvider.GetTimestampAsync(request, logger, new CancellationToken(canceled: true)));
+
+                Assert.Equal(OperationCancelledExceptionMessage, exception.Message);
             }
         }
 
diff --git a/test/NuGet.Core.Tests/NuGet.Commands.Test/RestoreCommandTests.cs b/test/NuGet.Core.Tests/NuGet.Commands.Test/RestoreCommandTests.cs
index 814cb2da9ad..4171be37257 100644
--- a/test/NuGet.Core.Tests/NuGet.Commands.Test/RestoreCommandTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Commands.Test/RestoreCommandTests.cs
@@ -969,7 +969,7 @@ public async Task RestoreCommand_ImportsNoMatchAsync()
             }
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public async Task RestoreCommand_InvalidSignedPackageAsync()
         {
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/PackageArchiveReaderTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/PackageArchiveReaderTests.cs
index 1c369ffca76..f379f70d151 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/PackageArchiveReaderTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/PackageArchiveReaderTests.cs
@@ -1597,7 +1597,7 @@ await Assert.ThrowsAsync<NotImplementedException>(
             }
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public async Task ValidateIntegrityAsync_WhenSignatureContentNull_Throws()
         {
@@ -1835,7 +1835,7 @@ public void GetContentHash_UnsignedPackage_WhenGivingAFallbackFunctionThatReturn
             }
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [CIOnlyFact]
         public async Task GetContentHash_IsSameForUnsignedAndSignedPackageAsync()
         {
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/AttributeUtilityTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/AttributeUtilityTests.cs
index 382231920b7..c4eb8b83871 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/AttributeUtilityTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/AttributeUtilityTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System;
 using System.Linq;
 using System.Security.Cryptography;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdTests.cs
index c63c07cb875..25e39bf9cb7 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdTests.cs
@@ -36,7 +36,7 @@ public void Read_WithInvalidAsn1_Throws()
                 () => EssCertId.Read(new byte[] { 0x30, 0x0b }));
         }
 
-#if !IS_CORECLR
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public void Read_WithValidInput_ReturnsEssCertId()
         {
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdV2Tests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdV2Tests.cs
index 7969df8bfd9..9d005a41aac 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdV2Tests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/EssCertIdV2Tests.cs
@@ -168,7 +168,7 @@ public void Read_WithNonDefaultAlgorithmIdentifier_ReturnsEssCertIdV2()
             SigningTestUtility.VerifyByteArrays(bcIssuerSerial.Serial.Value.ToByteArray(), essCertIdV2.IssuerSerial.SerialNumber);
         }
 
-#if !IS_CORECLR
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public void Read_WithValidInput_ReturnsEssCertId()
         {
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/PrimarySignatureTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/PrimarySignatureTests.cs
index 39199bc84e9..6a16317678a 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/PrimarySignatureTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/PrimarySignatureTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System;
 using System.Security.Cryptography.Pkcs;
 using System.Security.Cryptography.X509Certificates;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/ReadOnlyBufferedStreamTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/ReadOnlyBufferedStreamTests.cs
index e693f00c2d1..020abfd9bdf 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/ReadOnlyBufferedStreamTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/ReadOnlyBufferedStreamTests.cs
@@ -249,7 +249,7 @@ public void WriteTimeout_Setter_SetsValueOnUnderlyingStream()
             }
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public void Close_WhenLeaveOpenFalse_DisposesUnderlyingStream()
         {
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/RepositoryCountersignatureTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/RepositoryCountersignatureTests.cs
index 20a18861eb0..8c34ef7f080 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/RepositoryCountersignatureTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/RepositoryCountersignatureTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureTrustAndValidityVerificationProviderTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureTrustAndValidityVerificationProviderTests.cs
index 5e6fd38a398..ad86d149397 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureTrustAndValidityVerificationProviderTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureTrustAndValidityVerificationProviderTests.cs
@@ -14,7 +14,7 @@ namespace NuGet.Packaging.Test
 {
     public class SignatureTrustAndValidityVerificationProviderTests
     {
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         private static readonly Lazy<PrimarySignature> _signature = new Lazy<PrimarySignature>(
             () => PrimarySignature.Load(SigningTestUtility.GetResourceBytes(".signature.p7s")));
 #endif
@@ -25,7 +25,7 @@ public SignatureTrustAndValidityVerificationProviderTests()
             _provider = new SignatureTrustAndValidityVerificationProvider();
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public async Task GetTrustResultAsync_WhenPackageIsNull_Throws()
         {
@@ -53,7 +53,7 @@ public async Task GetTrustResultAsync_WhenSignatureIsNull_Throws()
             Assert.Equal("signature", exception.ParamName);
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public async Task GetTrustResultAsync_WhenSettingsIsNull_Throws()
         {
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureUtilityTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureUtilityTests.cs
index 1607159a045..3a0c06797e6 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureUtilityTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignatureUtilityTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System;
 using System.IO;
 using System.Threading;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveIOUtilityTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveIOUtilityTests.cs
index c911cd72d24..8f9e003d53b 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveIOUtilityTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveIOUtilityTests.cs
@@ -165,7 +165,7 @@ public void ReadAndHashUntilPosition_WhenPositionBeforeCurrentReadPosition_Throw
             }
         }
 
-#if !IS_CORECLR
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public void ReadAndHashUntilPosition_WhenPositionAtStart_ReadsAndHashes()
         {
@@ -248,7 +248,7 @@ public void HashBytes_WhenBytesNullOrEmpty_Throws(byte[] bytes)
             }
         }
 
-#if !IS_CORECLR
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public void HashBytes_WithInputBytes_Hashes()
         {
@@ -486,7 +486,7 @@ protected override void Dispose(bool disposing)
 
             internal string GetHash()
             {
-#if !IS_CORECLR
+#if IS_SIGNING_SUPPORTED
                 HashAlgorithm.TransformFinalBlock(new byte[0], inputOffset: 0, inputCount: 0);
 
                 return Convert.ToBase64String(HashAlgorithm.Hash);
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveTests.cs
index f8fa6c9aaac..40969f77eaf 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveUtilityTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveUtilityTests.cs
index ff6ab82aedb..a3644f6353f 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveUtilityTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SignedPackageArchiveUtilityTests.cs
@@ -257,7 +257,7 @@ public void GetPackageContentHash_WithCompressedSignatureFileEntry_NotThrows()
             }
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public async Task RemoveRepositorySignaturesAsync_WithNullInput_Throws()
         {
@@ -542,7 +542,7 @@ public void Dispose()
             }
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         private sealed class RemoveTest : IDisposable
         {
             private bool _isDisposed;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningOptionsTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningOptionsTests.cs
index a032b558bba..4902b2eb6f0 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningOptionsTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningOptionsTests.cs
@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System;
 using System.IO;
 using Moq;
diff --git a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningUtilityTests.cs b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningUtilityTests.cs
index 16edf8e21cb..f86e807678c 100644
--- a/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningUtilityTests.cs
+++ b/test/NuGet.Core.Tests/NuGet.Packaging.Test/SigningTests/SigningUtilityTests.cs
@@ -6,7 +6,7 @@
 using System.IO;
 using System.IO.Compression;
 using System.Linq;
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
 using System.Security.Cryptography.Pkcs;
 #endif
 using System.Security.Cryptography.X509Certificates;
@@ -159,7 +159,7 @@ public void Verify_WithUntrustedSelfSignedCertificate_Succeeds()
 
         }
 
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         [Fact]
         public void CreateSignedAttributes_SignPackageRequest_WhenRequestNull_Throws()
         {
diff --git a/test/TestUtilities/Test.Utility/Signing/SigningTestUtility.cs b/test/TestUtilities/Test.Utility/Signing/SigningTestUtility.cs
index 04110c535fb..06320b13b2f 100644
--- a/test/TestUtilities/Test.Utility/Signing/SigningTestUtility.cs
+++ b/test/TestUtilities/Test.Utility/Signing/SigningTestUtility.cs
@@ -496,7 +496,7 @@ public static SignedCms GenerateSignedCms(X509Certificate2 cert, byte[] content)
 
             return cms;
         }
-#if IS_DESKTOP
+#if IS_SIGNING_SUPPORTED
         /// <summary>
         /// Generates a SignedCMS object for some content.
         /// </summary>