diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 76c75882..97043007 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -15,6 +15,12 @@ updates:
         patterns:
           - "NUnit*"
           - "coverlet*"
+    ignore:
+      # 6.3.x makes Microsoft.Testing.Extensions.CodeCoverage statically
+      # instrument every DLL under the repo root instead of the test bin dir,
+      # so parallel test hosts rewrite each other's binaries and CI hangs.
+      - dependency-name: "NUnit3TestAdapter"
+        versions: ["6.3.0", "6.3.1"]
 
   - package-ecosystem: github-actions
     directory: /
diff --git a/Directory.Packages.props b/Directory.Packages.props
index dd74b353..49b907bd 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -9,7 +9,7 @@
     <PackageVersion Include="BenchmarkDotNet" Version="0.15.8" />
     <PackageVersion Include="FsCheck" Version="3.4.0" />
     <PackageVersion Include="FsCheck.NUnit" Version="3.0.0-rc3" />
-    <PackageVersion Include="NUnit" Version="4.6.1" />
+    <PackageVersion Include="NUnit" Version="5.0.0" />
     <PackageVersion Include="NUnit3TestAdapter" Version="6.2.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.11.0" />
     <!-- Explicit version to fix NUnit3TestAdapter binding issue -->
diff --git a/tests/SharpDicom.Codecs.Tests/NativeCodecsTests.cs b/tests/SharpDicom.Codecs.Tests/NativeCodecsTests.cs
index 5f89dec5..c0ba0db0 100644
--- a/tests/SharpDicom.Codecs.Tests/NativeCodecsTests.cs
+++ b/tests/SharpDicom.Codecs.Tests/NativeCodecsTests.cs
@@ -43,7 +43,6 @@ public void IsAvailable_BeforeInitialize_ReturnsFalse()
 #if NET5_0_OR_GREATER
         [Test]
         [Category("NativeCodecs")]
-        [Order(0)] // Run this test first to check initialization before other tests
         public void InitializeWithCustomPath_WhenLibraryExists_Succeeds()
         {
             // This test explicitly passes the library path to Initialize
diff --git a/tests/SharpDicom.Tests/Cli/LintCommandTests.cs b/tests/SharpDicom.Tests/Cli/LintCommandTests.cs
index cfd8aeb0..a298369c 100644
--- a/tests/SharpDicom.Tests/Cli/LintCommandTests.cs
+++ b/tests/SharpDicom.Tests/Cli/LintCommandTests.cs
@@ -122,7 +122,7 @@ public async Task InvalidUidFile_StrictProfile_ThrowsOnError()
         };
 
         // Strict mode throws on invalid UIDs rather than collecting them
-        Assert.ThrowsAsync<SharpDicom.Data.Exceptions.DicomDataException>(
+        await Assert.ThrowsAsync<SharpDicom.Data.Exceptions.DicomDataException>(
             async () => await DicomFile.OpenAsync(path, options));
     }
 
diff --git a/tests/SharpDicom.Tests/Deidentification/BatchDeidentifierTests.cs b/tests/SharpDicom.Tests/Deidentification/BatchDeidentifierTests.cs
index eda38df7..1129b5bb 100644
--- a/tests/SharpDicom.Tests/Deidentification/BatchDeidentifierTests.cs
+++ b/tests/SharpDicom.Tests/Deidentification/BatchDeidentifierTests.cs
@@ -391,7 +391,7 @@ public async Task BatchDeidentifier_InvalidInputDir_ThrowsDirectoryNotFoundExcep
         var config = DeidentificationConfigLoader.GetPreset("basic-profile");
         await using var batch = new BatchDeidentifier(_dbPath, config);
 
-        Assert.ThrowsAsync<DirectoryNotFoundException>(async () =>
+        await Assert.ThrowsAsync<DirectoryNotFoundException>(async () =>
         {
             await batch.ProcessDirectoryAsync("/nonexistent/path", _outputDir);
         });
diff --git a/tests/SharpDicom.Tests/IO/DicomFileReaderSequenceTests.cs b/tests/SharpDicom.Tests/IO/DicomFileReaderSequenceTests.cs
index 13859ffa..430f9725 100644
--- a/tests/SharpDicom.Tests/IO/DicomFileReaderSequenceTests.cs
+++ b/tests/SharpDicom.Tests/IO/DicomFileReaderSequenceTests.cs
@@ -58,7 +58,7 @@ public async Task ReadElementsAsync_FileWithSequence_YieldsSequenceElement()
 
             // Assert - should have the sequence
             Assert.That(elements, Has.Some.Matches<IDicomElement>(e =>
-                e.Tag == new DicomTag(0x0040, 0x0100) && e is DicomSequence));
+                e is DicomSequence sequence && sequence.Tag == new DicomTag(0x0040, 0x0100)));
         }
 
         [Test]
@@ -128,7 +128,7 @@ public async Task ReadElementsAsync_ImplicitVRFileWithSequence_ParsesCorrectly()
 
             // Assert - should have the sequence
             Assert.That(elements, Has.Some.Matches<IDicomElement>(e =>
-                e.Tag == new DicomTag(0x0040, 0x0100) && e is DicomSequence));
+                e is DicomSequence sequence && sequence.Tag == new DicomTag(0x0040, 0x0100)));
         }
 
         [Test]
diff --git a/tests/SharpDicom.Tests/IO/DicomFileReaderTests.cs b/tests/SharpDicom.Tests/IO/DicomFileReaderTests.cs
index d3059767..53340c04 100644
--- a/tests/SharpDicom.Tests/IO/DicomFileReaderTests.cs
+++ b/tests/SharpDicom.Tests/IO/DicomFileReaderTests.cs
@@ -38,7 +38,7 @@ public async Task ReadFileMetaInfoAsync_EmptyFile_Throws()
 
             await using var reader = new DicomFileReader(stream);
 
-            Assert.ThrowsAsync<DicomFileException>(async () =>
+            await Assert.ThrowsAsync<DicomFileException>(async () =>
                 await reader.ReadFileMetaInfoAsync());
         }
 
@@ -106,7 +106,7 @@ public async Task ReadElementsAsync_RespectsCancellation()
             cts.Cancel();
 
             // TaskCanceledException is a subclass of OperationCanceledException
-            var ex = Assert.CatchAsync<OperationCanceledException>(async () =>
+            var ex = await Assert.CatchAsync<OperationCanceledException>(async () =>
             {
                 await foreach (var _ in reader.ReadElementsAsync(cts.Token))
                 {
@@ -219,7 +219,7 @@ public async Task AfterDispose_ReadThrows()
             var reader = new DicomFileReader(stream);
             await reader.DisposeAsync();
 
-            Assert.ThrowsAsync<ObjectDisposedException>(async () =>
+            await Assert.ThrowsAsync<ObjectDisposedException>(async () =>
                 await reader.ReadFileMetaInfoAsync());
         }
 
diff --git a/tests/SharpDicom.Tests/IO/PixelDataSourceTests.cs b/tests/SharpDicom.Tests/IO/PixelDataSourceTests.cs
index c4a9af51..12aa1b62 100644
--- a/tests/SharpDicom.Tests/IO/PixelDataSourceTests.cs
+++ b/tests/SharpDicom.Tests/IO/PixelDataSourceTests.cs
@@ -354,24 +354,24 @@ public void SkippedPixelDataSource_GetData_ThrowsInvalidOperationException()
     }
 
     [Test]
-    public void SkippedPixelDataSource_GetDataAsync_ThrowsInvalidOperationException()
+    public async Task SkippedPixelDataSource_GetDataAsync_ThrowsInvalidOperationException()
     {
         // Arrange
         using var source = new SkippedPixelDataSource(0, 100);
 
         // Act & Assert
-        Assert.ThrowsAsync<InvalidOperationException>(async () => await source.GetDataAsync());
+        await Assert.ThrowsAsync<InvalidOperationException>(async () => await source.GetDataAsync());
     }
 
     [Test]
-    public void SkippedPixelDataSource_CopyToAsync_ThrowsInvalidOperationException()
+    public async Task SkippedPixelDataSource_CopyToAsync_ThrowsInvalidOperationException()
     {
         // Arrange
         using var source = new SkippedPixelDataSource(0, 100);
         using var destination = new MemoryStream();
 
         // Act & Assert
-        Assert.ThrowsAsync<InvalidOperationException>(async () => await source.CopyToAsync(destination));
+        await Assert.ThrowsAsync<InvalidOperationException>(async () => await source.CopyToAsync(destination));
     }
 
     [Test]
diff --git a/tests/SharpDicom.Tests/Integration/ImplicitVRSequenceTests.cs b/tests/SharpDicom.Tests/Integration/ImplicitVRSequenceTests.cs
index 335c5613..8c243cd1 100644
--- a/tests/SharpDicom.Tests/Integration/ImplicitVRSequenceTests.cs
+++ b/tests/SharpDicom.Tests/Integration/ImplicitVRSequenceTests.cs
@@ -141,14 +141,14 @@ public async Task Parse_NestedSequences_ParentChainCorrect()
     }
 
     [Test]
-    public void Parse_NestedSequences_ExceedsMaxDepth_ThrowsException()
+    public async Task Parse_NestedSequences_ExceedsMaxDepth_ThrowsException()
     {
         var data = CreateDeeplyNestedSequenceFile(10);
         using var stream = new MemoryStream(data);
 
         var options = new DicomReaderOptions { MaxSequenceDepth = 4 };
 
-        Assert.ThrowsAsync<DicomDataException>(async () =>
+        await Assert.ThrowsAsync<DicomDataException>(async () =>
         {
             await DicomFile.OpenAsync(stream, options);
         });
diff --git a/tests/SharpDicom.Tests/Network/CEchoTests.cs b/tests/SharpDicom.Tests/Network/CEchoTests.cs
index 03ea1a26..6b75d821 100644
--- a/tests/SharpDicom.Tests/Network/CEchoTests.cs
+++ b/tests/SharpDicom.Tests/Network/CEchoTests.cs
@@ -259,7 +259,7 @@ public async Task AssociationReject_ClientThrowsException()
             };
 
             // Act & Assert
-            var ex = Assert.ThrowsAsync<DicomAssociationException>(
+            var ex = await Assert.ThrowsAsync<DicomAssociationException>(
                 async () => await client.ConnectAsync(contexts));
 
             Assert.That(ex, Is.Not.Null);
@@ -281,7 +281,7 @@ public async Task CEchoAsync_BeforeConnect_ThrowsException()
             await using var client = new DicomClient(clientOptions);
 
             // Act & Assert
-            var ex = Assert.ThrowsAsync<DicomAssociationException>(
+            var ex = await Assert.ThrowsAsync<DicomAssociationException>(
                 async () => await client.CEchoAsync());
 
             Assert.That(ex, Is.Not.Null);
@@ -326,7 +326,7 @@ public async Task CEchoAsync_VerificationNotNegotiated_ThrowsException()
             await client.ConnectAsync(contexts);
 
             // Act & Assert - C-ECHO should fail because Verification SOP Class not negotiated
-            var ex = Assert.ThrowsAsync<DicomAssociationException>(
+            var ex = await Assert.ThrowsAsync<DicomAssociationException>(
                 async () => await client.CEchoAsync());
 
             Assert.That(ex, Is.Not.Null);
diff --git a/tests/SharpDicom.Tests/Network/DicomClientTests.cs b/tests/SharpDicom.Tests/Network/DicomClientTests.cs
index a4d55992..c46a5e66 100644
--- a/tests/SharpDicom.Tests/Network/DicomClientTests.cs
+++ b/tests/SharpDicom.Tests/Network/DicomClientTests.cs
@@ -290,7 +290,7 @@ public async Task ConnectAsync_AfterDispose_ThrowsObjectDisposedException()
                 new PresentationContext(1, DicomUID.Verification, TransferSyntax.ImplicitVRLittleEndian)
             };
 
-            Assert.ThrowsAsync<ObjectDisposedException>(
+            await Assert.ThrowsAsync<ObjectDisposedException>(
                 async () => await client.ConnectAsync(contexts));
         }
 
@@ -301,7 +301,7 @@ public async Task CEchoAsync_AfterDispose_ThrowsObjectDisposedException()
             var client = new DicomClient(options);
             await client.DisposeAsync();
 
-            Assert.ThrowsAsync<ObjectDisposedException>(
+            await Assert.ThrowsAsync<ObjectDisposedException>(
                 async () => await client.CEchoAsync());
         }
 
diff --git a/tests/SharpDicom.Tests/Network/Tls/TlsIntegrationTests.cs b/tests/SharpDicom.Tests/Network/Tls/TlsIntegrationTests.cs
index 232be517..0c24e8fe 100644
--- a/tests/SharpDicom.Tests/Network/Tls/TlsIntegrationTests.cs
+++ b/tests/SharpDicom.Tests/Network/Tls/TlsIntegrationTests.cs
@@ -429,7 +429,7 @@ public async Task SelfSigned_AcceptedViaThumbprint()
         }
 
         [Test]
-        public void SelfSigned_RejectedWithoutThumbprint()
+        public async Task SelfSigned_RejectedWithoutThumbprint()
         {
             // Arrange
             var serverCert = TlsCertificateHelper.CreateSelfSignedCertificate("localhost", TimeSpan.FromHours(1));
@@ -450,7 +450,7 @@ public void SelfSigned_RejectedWithoutThumbprint()
 
             var server = new DicomServer(serverOptions);
             server.Start();
-            Task.Delay(100).Wait();
+            await Task.Delay(100);
 
             try
             {
@@ -476,7 +476,7 @@ public void SelfSigned_RejectedWithoutThumbprint()
                 };
 
                 // Act & Assert
-                Assert.ThrowsAsync<TlsHandshakeException>(async () =>
+                await Assert.ThrowsAsync<TlsHandshakeException>(async () =>
                 {
                     await using (client)
                     {
@@ -561,7 +561,7 @@ public async Task CustomCA_AcceptedWithCAInTrustStore()
 
 #if NET6_0_OR_GREATER
         [Test]
-        public void MutualTls_MissingClientCert_Fails()
+        public async Task MutualTls_MissingClientCert_Fails()
         {
             // Arrange
             using var serverCert = TlsCertificateHelper.CreateSelfSignedCertificate("localhost", TimeSpan.FromHours(1));
@@ -584,7 +584,7 @@ public void MutualTls_MissingClientCert_Fails()
 
             var server = new DicomServer(serverOptions);
             server.Start();
-            Task.Delay(100).Wait();
+            await Task.Delay(100);
 
             try
             {
@@ -612,7 +612,7 @@ public void MutualTls_MissingClientCert_Fails()
 
                 // Act & Assert - Server will close connection when client doesn't provide cert
                 // This can manifest as TlsHandshakeException or EndOfStreamException
-                Assert.CatchAsync<Exception>(async () =>
+                await Assert.CatchAsync<Exception>(async () =>
                 {
                     await using (client)
                     {
@@ -628,7 +628,7 @@ public void MutualTls_MissingClientCert_Fails()
         }
 
         [Test]
-        public void InvalidCert_Rejected()
+        public async Task InvalidCert_Rejected()
         {
             // Arrange - Use expired certificate
             var expiredCert = TlsCertificateHelper.CreateExpiredCertificate("localhost");
@@ -649,7 +649,7 @@ public void InvalidCert_Rejected()
 
             var server = new DicomServer(serverOptions);
             server.Start();
-            Task.Delay(100).Wait();
+            await Task.Delay(100);
 
             try
             {
@@ -675,7 +675,7 @@ public void InvalidCert_Rejected()
                 };
 
                 // Act & Assert
-                var ex = Assert.ThrowsAsync<TlsHandshakeException>(async () =>
+                var ex = await Assert.ThrowsAsync<TlsHandshakeException>(async () =>
                 {
                     await using (client)
                     {