diff --git a/test/CloudNative.CloudEvents.UnitTests/CloudEventsSpecVersionTest.cs b/test/CloudNative.CloudEvents.UnitTests/CloudEventsSpecVersionTest.cs
index 4d8252b..4701f06 100644
--- a/test/CloudNative.CloudEvents.UnitTests/CloudEventsSpecVersionTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/CloudEventsSpecVersionTest.cs
@@ -1,4 +1,4 @@
-// Copyright 2021 Cloud Native Foundation. 
+// Copyright 2021 Cloud Native Foundation. 
 // Licensed under the Apache 2.0 license.
 // See LICENSE file in the project root for full license information.
 
@@ -13,7 +13,7 @@ namespace CloudNative.CloudEvents.UnitTests
         [InlineData(null)]
         [InlineData("bogus")]
         [InlineData("1")]
-        public void FromVersionId_Unknown(string versionId) =>
+        public void FromVersionId_Unknown(string? versionId) =>
             Assert.Null(CloudEventsSpecVersion.FromVersionId(versionId));
 
         [Theory]
diff --git a/test/CloudNative.CloudEvents.UnitTests/Core/MimeUtilitiesTest.cs b/test/CloudNative.CloudEvents.UnitTests/Core/MimeUtilitiesTest.cs
index 8e053ff..e7c18bd 100644
--- a/test/CloudNative.CloudEvents.UnitTests/Core/MimeUtilitiesTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/Core/MimeUtilitiesTest.cs
@@ -1,4 +1,4 @@
-// Copyright 2021 Cloud Native Foundation. 
+// Copyright 2021 Cloud Native Foundation. 
 // Licensed under the Apache 2.0 license.
 // See LICENSE file in the project root for full license information.
 
@@ -73,7 +73,7 @@ namespace CloudNative.CloudEvents.Core.UnitTests
         [Theory]
         [InlineData(null)]
         [InlineData("text/plain")]
-        public void CreateContentTypeOrNull_WithContentType(string text)
+        public void CreateContentTypeOrNull_WithContentType(string? text)
         {
             ContentType? ct = MimeUtilities.CreateContentTypeOrNull(text);
             Assert.Equal(text, ct?.ToString());
@@ -88,7 +88,7 @@ namespace CloudNative.CloudEvents.Core.UnitTests
         [InlineData("application/cloudeventstrailing", true)]
         [InlineData("application/cloudevents-batch", false)]
         [InlineData("application/cloudevents-batch+json", false)]
-        public void IsCloudEventsContentType(string contentType, bool expectedResult) =>
+        public void IsCloudEventsContentType(string? contentType, bool expectedResult) =>
             Assert.Equal(expectedResult, MimeUtilities.IsCloudEventsContentType(contentType));
 
         [Theory]
@@ -101,7 +101,7 @@ namespace CloudNative.CloudEvents.Core.UnitTests
         // It's not entirely clear that this *should* be true...
         [InlineData("application/cloudevents-batchtrailing", true)]
         [InlineData("application/cloudevents-batch+json", true)]
-        public void IsCloudEventsBatchContentType(string contentType, bool expectedResult) =>
+        public void IsCloudEventsBatchContentType(string? contentType, bool expectedResult) =>
             Assert.Equal(expectedResult, MimeUtilities.IsCloudEventsBatchContentType(contentType));
     }
 }
diff --git a/test/CloudNative.CloudEvents.UnitTests/Http/HttpClientExtensionsTest.cs b/test/CloudNative.CloudEvents.UnitTests/Http/HttpClientExtensionsTest.cs
index d711a80..de77f8d 100644
--- a/test/CloudNative.CloudEvents.UnitTests/Http/HttpClientExtensionsTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/Http/HttpClientExtensionsTest.cs
@@ -1,4 +1,4 @@
-// Copyright 2021 Cloud Native Foundation. 
+// Copyright 2021 Cloud Native Foundation. 
 // Licensed under the Apache 2.0 license.
 // See LICENSE file in the project root for full license information.
 
@@ -291,7 +291,7 @@ namespace CloudNative.CloudEvents.Http.UnitTests
             var result = await httpClient.PostAsync(new Uri(ListenerAddress + "ep"), content);
             if (result.StatusCode != HttpStatusCode.NoContent)
             {
-                throw new InvalidOperationException(result.Content.ReadAsStringAsync().GetAwaiter().GetResult());
+                throw new InvalidOperationException(await result.Content.ReadAsStringAsync());
             }
         }
 
@@ -392,7 +392,7 @@ namespace CloudNative.CloudEvents.Http.UnitTests
             var result = (await httpClient.PostAsync(new Uri(ListenerAddress + "ep"), content));
             if (result.StatusCode != HttpStatusCode.NoContent)
             {
-                throw new InvalidOperationException(result.Content.ReadAsStringAsync().GetAwaiter().GetResult());
+                throw new InvalidOperationException(await result.Content.ReadAsStringAsync());
             }
         }
 
diff --git a/test/CloudNative.CloudEvents.UnitTests/Kafka/KafkaTest.cs b/test/CloudNative.CloudEvents.UnitTests/Kafka/KafkaTest.cs
index 7d1b258..b8bcc0c 100644
--- a/test/CloudNative.CloudEvents.UnitTests/Kafka/KafkaTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/Kafka/KafkaTest.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Cloud Native Foundation.
+// Copyright (c) Cloud Native Foundation.
 // Licensed under the Apache 2.0 license.
 // See LICENSE file in the project root for full license information.
 
@@ -135,7 +135,7 @@ namespace CloudNative.CloudEvents.Kafka.UnitTests
         [InlineData(MediaTypeNames.Application.Xml, "")]
         [InlineData(MediaTypeNames.Text.Plain, "")]
         [InlineData(null, null)]
-        public void KafkaBinaryMessageTombstoneTest(string contentType, object? expectedDecodedResult)
+        public void KafkaBinaryMessageTombstoneTest(string? contentType, object? expectedDecodedResult)
         {
             var jsonEventFormatter = new JsonEventFormatter();
             var cloudEvent = new CloudEvent(Partitioning.AllAttributes)
@@ -253,4 +253,4 @@ namespace CloudNative.CloudEvents.Kafka.UnitTests
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/test/CloudNative.CloudEvents.UnitTests/NewtonsoftJson/JsonEventFormatterTest.cs b/test/CloudNative.CloudEvents.UnitTests/NewtonsoftJson/JsonEventFormatterTest.cs
index f0abb62..4ae806a 100644
--- a/test/CloudNative.CloudEvents.UnitTests/NewtonsoftJson/JsonEventFormatterTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/NewtonsoftJson/JsonEventFormatterTest.cs
@@ -706,7 +706,7 @@ namespace CloudNative.CloudEvents.NewtonsoftJson.UnitTests
         [InlineData("application/json")]
         [InlineData("text/plain")]
         [InlineData("application/binary")]
-        public void DecodeStructuredModeMessage_NoData(string contentType)
+        public void DecodeStructuredModeMessage_NoData(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -740,7 +740,7 @@ namespace CloudNative.CloudEvents.NewtonsoftJson.UnitTests
         [InlineData("application/json")]
         [InlineData("text/plain")]
         [InlineData("application/binary")]
-        public void DecodeStructuredModeMessage_Base64(string contentType)
+        public void DecodeStructuredModeMessage_Base64(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -768,7 +768,7 @@ namespace CloudNative.CloudEvents.NewtonsoftJson.UnitTests
         [InlineData(null)]
         [InlineData("application/json")]
         [InlineData("application/json; charset=utf-8")]
-        public void DecodeStructuredModeMessage_JsonContentType_JsonStringToken(string contentType)
+        public void DecodeStructuredModeMessage_JsonContentType_JsonStringToken(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -787,7 +787,7 @@ namespace CloudNative.CloudEvents.NewtonsoftJson.UnitTests
         [InlineData("application/json")]
         [InlineData("application/xyz+json")]
         [InlineData("application/xyz+json; charset=utf-8")]
-        public void DecodeStructuredModeMessage_JsonContentType_NonStringValue(string contentType)
+        public void DecodeStructuredModeMessage_JsonContentType_NonStringValue(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -1215,4 +1215,4 @@ namespace CloudNative.CloudEvents.NewtonsoftJson.UnitTests
             return formatter.DecodeBatchModeMessage(bytes, s_jsonCloudEventContentType, null);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/test/CloudNative.CloudEvents.UnitTests/Protobuf/ProtobufEventFormatterTest.cs b/test/CloudNative.CloudEvents.UnitTests/Protobuf/ProtobufEventFormatterTest.cs
index 087c2da..9868d2a 100644
--- a/test/CloudNative.CloudEvents.UnitTests/Protobuf/ProtobufEventFormatterTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/Protobuf/ProtobufEventFormatterTest.cs
@@ -1,4 +1,4 @@
-// Copyright 2022 Cloud Native Foundation. 
+// Copyright 2022 Cloud Native Foundation. 
 // Licensed under the Apache 2.0 license.
 // See LICENSE file in the project root for full license information.
 
@@ -201,7 +201,7 @@ namespace CloudNative.CloudEvents.Protobuf.UnitTests
         [InlineData("utf-8")]
         [InlineData("iso-8859-1")]
         [InlineData(null)]
-        public void EncodeBinaryModeData_String_TextContentType(string charset)
+        public void EncodeBinaryModeData_String_TextContentType(string? charset)
         {
             string text = "caf\u00e9"; // Valid in both UTF-8 and ISO-8859-1, but with different representations
             var encoding = charset is null ? Encoding.UTF8 : Encoding.GetEncoding(charset);
@@ -552,7 +552,7 @@ namespace CloudNative.CloudEvents.Protobuf.UnitTests
         [InlineData("utf-8")]
         [InlineData("iso-8859-1")]
         [InlineData(null)]
-        public void DecodeBinaryModeEventData_Text(string charset)
+        public void DecodeBinaryModeEventData_Text(string? charset)
         {
             string text = "caf\u00e9"; // Valid in both UTF-8 and ISO-8859-1, but with different representations
             var encoding = charset is null ? Encoding.UTF8 : Encoding.GetEncoding(charset);
@@ -566,7 +566,7 @@ namespace CloudNative.CloudEvents.Protobuf.UnitTests
         [Theory]
         [InlineData("application/json")]
         [InlineData(null)]
-        public void DecodeBinaryModeData_NonTextContentType(string contentType)
+        public void DecodeBinaryModeData_NonTextContentType(string? contentType)
         {
             var bytes = Encoding.UTF8.GetBytes("{}");
             var data = DecodeBinaryModeEventData(bytes, contentType);
@@ -670,7 +670,7 @@ namespace CloudNative.CloudEvents.Protobuf.UnitTests
 
         // Utility methods
 
-        private static object? DecodeBinaryModeEventData(byte[] bytes, string contentType)
+        private static object? DecodeBinaryModeEventData(byte[] bytes, string? contentType)
         {
             var cloudEvent = new CloudEvent().PopulateRequiredAttributes();
             cloudEvent.DataContentType = contentType;
diff --git a/test/CloudNative.CloudEvents.UnitTests/SystemTextJson/JsonEventFormatterTest.cs b/test/CloudNative.CloudEvents.UnitTests/SystemTextJson/JsonEventFormatterTest.cs
index af1ef0c..888639f 100644
--- a/test/CloudNative.CloudEvents.UnitTests/SystemTextJson/JsonEventFormatterTest.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/SystemTextJson/JsonEventFormatterTest.cs
@@ -726,7 +726,7 @@ namespace CloudNative.CloudEvents.SystemTextJson.UnitTests
         [InlineData("application/json")]
         [InlineData("text/plain")]
         [InlineData("application/binary")]
-        public void DecodeStructuredModeMessage_NoData(string contentType)
+        public void DecodeStructuredModeMessage_NoData(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -760,7 +760,7 @@ namespace CloudNative.CloudEvents.SystemTextJson.UnitTests
         [InlineData("application/json")]
         [InlineData("text/plain")]
         [InlineData("application/binary")]
-        public void DecodeStructuredModeMessage_Base64(string contentType)
+        public void DecodeStructuredModeMessage_Base64(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -788,7 +788,7 @@ namespace CloudNative.CloudEvents.SystemTextJson.UnitTests
         [InlineData(null)]
         [InlineData("application/json")]
         [InlineData("application/json; charset=utf-8")]
-        public void DecodeStructuredModeMessage_JsonContentType_JsonStringToken(string contentType)
+        public void DecodeStructuredModeMessage_JsonContentType_JsonStringToken(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -807,7 +807,7 @@ namespace CloudNative.CloudEvents.SystemTextJson.UnitTests
         [InlineData("application/json")]
         [InlineData("application/xyz+json")]
         [InlineData("application/xyz+json; charset=utf-8")]
-        public void DecodeStructuredModeMessage_JsonContentType_NonStringValue(string contentType)
+        public void DecodeStructuredModeMessage_JsonContentType_NonStringValue(string? contentType)
         {
             var obj = CreateMinimalValidJObject();
             if (contentType is object)
@@ -1227,4 +1227,4 @@ namespace CloudNative.CloudEvents.SystemTextJson.UnitTests
                 writer.WriteStringValue(value.ToString("yyyy-MM-dd", CultureInfo.InvariantCulture));
         }
     }
-}
\ No newline at end of file
+}
diff --git a/test/CloudNative.CloudEvents.UnitTests/TestHelpers.cs b/test/CloudNative.CloudEvents.UnitTests/TestHelpers.cs
index da1d230..f21bfee 100644
--- a/test/CloudNative.CloudEvents.UnitTests/TestHelpers.cs
+++ b/test/CloudNative.CloudEvents.UnitTests/TestHelpers.cs
@@ -1,4 +1,4 @@
-// Copyright 2021 Cloud Native Foundation. 
+// Copyright 2021 Cloud Native Foundation. 
 // Licensed under the Apache 2.0 license.
 // See LICENSE file in the project root for full license information.
 
@@ -153,7 +153,7 @@ namespace CloudNative.CloudEvents.UnitTests
             }
             if (expected is null || actual is null)
             {
-                Assert.True(false, "Expected both values to be null, or neither to be null");
+                Assert.Fail("Expected both values to be null, or neither to be null");
             }
             AssertTimestampsEqual(expected!.Value, actual!.Value);
         }