diff --git a/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs b/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs
index 59088ce0877..355ab376743 100644
--- a/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs
+++ b/src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs
@@ -30,7 +30,7 @@ public class OtlpExporterOptions : IOtlpExporterOptions
 
     internal static readonly KeyValuePair<string, string>[] StandardHeaders = new KeyValuePair<string, string>[]
     {
-        new KeyValuePair<string, string>("User-Agent", GetUserAgentString()),
+        new("User-Agent", GetUserAgentString()),
     };
 
     internal readonly Func<HttpClient> DefaultHttpClientFactory;
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/BaseOtlpHttpExportClientTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/BaseOtlpHttpExportClientTests.cs
index a846af33a4e..36d534df9a1 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/BaseOtlpHttpExportClientTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/BaseOtlpHttpExportClientTests.cs
@@ -17,7 +17,7 @@ public class BaseOtlpHttpExportClientTests
     [InlineData("https://custom.host", null, "https://custom.host")]
     [InlineData("http://custom.host:44318/custom/path", null, "http://custom.host:44318/custom/path")]
     [InlineData("https://custom.host", "http://from.otel.exporter.env.var", "https://custom.host")]
-    public void ValidateOtlpHttpExportClientEndpoint(string optionEndpoint, string endpointEnvVar, string expectedExporterEndpoint)
+    public void ValidateOtlpHttpExportClientEndpoint(string? optionEndpoint, string? endpointEnvVar, string expectedExporterEndpoint)
     {
         try
         {
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/Implementation/ExportClient/OtlpHttpTraceExportClientTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/Implementation/ExportClient/OtlpHttpTraceExportClientTests.cs
index d796e36ef5a..0b932f87d39 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/Implementation/ExportClient/OtlpHttpTraceExportClientTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/Implementation/ExportClient/OtlpHttpTraceExportClientTests.cs
@@ -63,8 +63,8 @@ public void NewOtlpHttpTraceExportClient_OtlpExporterOptions_ExporterHasCorrectP
     public void SendExportRequest_ExportTraceServiceRequest_SendsCorrectHttpRequest(bool includeServiceNameInResource)
     {
         // Arrange
-        var evenTags = new[] { new KeyValuePair<string, object>("k0", "v0") };
-        var oddTags = new[] { new KeyValuePair<string, object>("k1", "v1") };
+        var evenTags = new[] { new KeyValuePair<string, object?>("k0", "v0") };
+        var oddTags = new[] { new KeyValuePair<string, object?>("k1", "v1") };
         var sources = new[]
         {
             new ActivitySource("even", "2.4.6"),
@@ -116,7 +116,8 @@ public void SendExportRequest_ExportTraceServiceRequest_SendsCorrectHttpRequest(
             var activityKind = isEven ? ActivityKind.Client : ActivityKind.Server;
             var activityTags = isEven ? evenTags : oddTags;
 
-            using Activity activity = source.StartActivity($"span-{i}", activityKind, parentContext: default, activityTags);
+            using Activity? activity = source.StartActivity($"span-{i}", activityKind, parentContext: default, activityTags);
+            Assert.NotNull(activity);
             processor.OnEnd(activity);
         }
 
@@ -141,6 +142,7 @@ void RunTest(Batch<Activity> batch)
             Assert.True(result.Success);
             Assert.NotNull(httpRequest);
             Assert.Equal(HttpMethod.Post, httpRequest.Method);
+            Assert.NotNull(httpRequest.RequestUri);
             Assert.Equal("http://localhost:4317/", httpRequest.RequestUri.AbsoluteUri);
             Assert.Equal(OtlpExporterOptions.StandardHeaders.Length + 2, httpRequest.Headers.Count());
             Assert.Contains(httpRequest.Headers, h => h.Key == header1.Name && h.Value.First() == header1.Value);
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/IntegrationTest/IntegrationTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/IntegrationTest/IntegrationTests.cs
index 14b73571e35..3e40b9c6d9f 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/IntegrationTest/IntegrationTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/IntegrationTest/IntegrationTests.cs
@@ -21,7 +21,7 @@ public sealed class IntegrationTests : IDisposable
     private const int ExportIntervalMilliseconds = 10000;
     private static readonly SdkLimitOptions DefaultSdkLimitOptions = new();
     private static readonly ExperimentalOptions DefaultExperimentalOptions = new();
-    private static readonly string CollectorHostname = SkipUnlessEnvVarFoundTheoryAttribute.GetEnvironmentVariable(CollectorHostnameEnvVarName);
+    private static readonly string? CollectorHostname = SkipUnlessEnvVarFoundTheoryAttribute.GetEnvironmentVariable(CollectorHostnameEnvVarName);
     private readonly OpenTelemetryEventListener openTelemetryEventListener;
 
     public IntegrationTests(ITestOutputHelper outputHelper)
@@ -61,7 +61,7 @@ public void TraceExportResultIsSuccess(OtlpExportProtocol protocol, string endpo
             },
         };
 
-        DelegatingExporter<Activity> delegatingExporter = null;
+        DelegatingExporter<Activity>? delegatingExporter = null;
         var exportResults = new List<ExportResult>();
 
         var activitySourceName = "otlp.collector.test";
@@ -140,7 +140,7 @@ public void MetricExportResultIsSuccess(OtlpExportProtocol protocol, string endp
             Protocol = protocol,
         };
 
-        DelegatingExporter<Metric> delegatingExporter = null;
+        DelegatingExporter<Metric>? delegatingExporter = null;
         var exportResults = new List<ExportResult>();
 
         var meterName = "otlp.collector.test";
@@ -220,7 +220,7 @@ public void LogExportResultIsSuccess(OtlpExportProtocol protocol, string endpoin
             Protocol = protocol,
         };
 
-        DelegatingExporter<LogRecord> delegatingExporter = null;
+        DelegatingExporter<LogRecord> delegatingExporter;
         var exportResults = new List<ExportResult>();
         var processorOptions = new LogRecordExportProcessorOptions
         {
@@ -298,8 +298,8 @@ protected override void OnEventSourceCreated(EventSource eventSource)
 
         protected override void OnEventWritten(EventWrittenEventArgs eventData)
         {
-            string message;
-            if (eventData.Message != null && (eventData.Payload?.Count ?? 0) > 0)
+            string? message;
+            if (eventData.Message != null && eventData.Payload != null && eventData.Payload.Count > 0)
             {
                 message = string.Format(eventData.Message, eventData.Payload.ToArray());
             }
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/MockCollectorIntegrationTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/MockCollectorIntegrationTests.cs
index a5ce7a0a279..e72a6773b81 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/MockCollectorIntegrationTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/MockCollectorIntegrationTests.cs
@@ -3,6 +3,7 @@
 
 #if !NETFRAMEWORK
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Net;
 using Google.Protobuf;
 using Grpc.Core;
@@ -94,12 +95,12 @@ public async Task TestRecoveryAfterFailedExport()
 
         using var source = new ActivitySource(activitySourceName);
 
-        source.StartActivity().Stop();
+        source.StartActivity()?.Stop();
 
         Assert.Single(exportResults);
         Assert.Equal(ExportResult.Failure, exportResults[0]);
 
-        source.StartActivity().Stop();
+        source.StartActivity()?.Stop();
 
         Assert.Equal(2, exportResults.Count);
         Assert.Equal(ExportResult.Success, exportResults[1]);
@@ -179,7 +180,7 @@ public async Task GrpcRetryTests(bool useRetryTransmissionHandler, ExportResult
         var exporterOptions = new OtlpExporterOptions() { Endpoint = endpoint, TimeoutMilliseconds = 20000, Protocol = OtlpExportProtocol.Grpc };
 
         var configuration = new ConfigurationBuilder()
-         .AddInMemoryCollection(new Dictionary<string, string> { [ExperimentalOptions.OtlpRetryEnvVar] = useRetryTransmissionHandler ? "in_memory" : null })
+         .AddInMemoryCollection(new Dictionary<string, string?> { [ExperimentalOptions.OtlpRetryEnvVar] = useRetryTransmissionHandler ? "in_memory" : null })
          .Build();
 
         var otlpExporter = new OtlpTraceExporter(exporterOptions, new SdkLimitOptions(), new ExperimentalOptions(configuration));
@@ -192,6 +193,7 @@ public async Task GrpcRetryTests(bool useRetryTransmissionHandler, ExportResult
             .Build();
 
         using var activity = source.StartActivity("GrpcRetryTest");
+        Assert.NotNull(activity);
         activity.Stop();
         using var batch = new Batch<Activity>([activity], 1);
 
@@ -263,7 +265,7 @@ public async Task HttpRetryTests(bool useRetryTransmissionHandler, ExportResult
         var exporterOptions = new OtlpExporterOptions() { Endpoint = endpoint, TimeoutMilliseconds = 20000, Protocol = OtlpExportProtocol.HttpProtobuf };
 
         var configuration = new ConfigurationBuilder()
-         .AddInMemoryCollection(new Dictionary<string, string> { [ExperimentalOptions.OtlpRetryEnvVar] = useRetryTransmissionHandler ? "in_memory" : null })
+         .AddInMemoryCollection(new Dictionary<string, string?> { [ExperimentalOptions.OtlpRetryEnvVar] = useRetryTransmissionHandler ? "in_memory" : null })
          .Build();
 
         var otlpExporter = new OtlpTraceExporter(exporterOptions, new SdkLimitOptions(), new ExperimentalOptions(configuration));
@@ -276,6 +278,7 @@ public async Task HttpRetryTests(bool useRetryTransmissionHandler, ExportResult
             .Build();
 
         using var activity = source.StartActivity("HttpRetryTest");
+        Assert.NotNull(activity);
         activity.Stop();
         using var batch = new Batch<Activity>([activity], 1);
 
@@ -348,7 +351,7 @@ public async Task HttpPersistentStorageRetryTests(bool usePersistentStorageTrans
 
         // TODO: update this to configure via experimental environment variable.
         OtlpExporterTransmissionHandler<ExportTraceServiceRequest> transmissionHandler;
-        MockFileProvider mockProvider = null;
+        MockFileProvider? mockProvider = null;
         if (usePersistentStorageTransmissionHandler)
         {
             mockProvider = new MockFileProvider();
@@ -378,6 +381,7 @@ public async Task HttpPersistentStorageRetryTests(bool usePersistentStorageTrans
             .Build();
 
         using var activity = source.StartActivity("HttpPersistentStorageRetryTest");
+        Assert.NotNull(activity);
         activity.Stop();
         using var batch = new Batch<Activity>([activity], 1);
 
@@ -387,12 +391,13 @@ public async Task HttpPersistentStorageRetryTests(bool usePersistentStorageTrans
 
         if (usePersistentStorageTransmissionHandler)
         {
+            Assert.NotNull(mockProvider);
             if (exportResult == ExportResult.Success)
             {
-                Assert.Single(mockProvider.TryGetBlobs());
+                Assert.Single(mockProvider!.TryGetBlobs());
 
                 // Force Retry
-                Assert.True((transmissionHandler as OtlpExporterPersistentStorageTransmissionHandler<ExportTraceServiceRequest>).InitiateAndWaitForRetryProcess(-1));
+                Assert.True((transmissionHandler as OtlpExporterPersistentStorageTransmissionHandler<ExportTraceServiceRequest>)!.InitiateAndWaitForRetryProcess(-1));
 
                 Assert.False(mockProvider.TryGetBlob(out _));
             }
@@ -485,7 +490,7 @@ public async Task GrpcPersistentStorageRetryTests(bool usePersistentStorageTrans
 
         // TODO: update this to configure via experimental environment variable.
         OtlpExporterTransmissionHandler<ExportTraceServiceRequest> transmissionHandler;
-        MockFileProvider mockProvider = null;
+        MockFileProvider? mockProvider = null;
         if (usePersistentStorageTransmissionHandler)
         {
             mockProvider = new MockFileProvider();
@@ -515,6 +520,7 @@ public async Task GrpcPersistentStorageRetryTests(bool usePersistentStorageTrans
             .Build();
 
         using var activity = source.StartActivity("GrpcPersistentStorageRetryTest");
+        Assert.NotNull(activity);
         activity.Stop();
         using var batch = new Batch<Activity>([activity], 1);
 
@@ -524,12 +530,13 @@ public async Task GrpcPersistentStorageRetryTests(bool usePersistentStorageTrans
 
         if (usePersistentStorageTransmissionHandler)
         {
+            Assert.NotNull(mockProvider);
             if (exportResult == ExportResult.Success)
             {
                 Assert.Single(mockProvider.TryGetBlobs());
 
                 // Force Retry
-                Assert.True((transmissionHandler as OtlpExporterPersistentStorageTransmissionHandler<ExportTraceServiceRequest>).InitiateAndWaitForRetryProcess(-1));
+                Assert.True((transmissionHandler as OtlpExporterPersistentStorageTransmissionHandler<ExportTraceServiceRequest>)!.InitiateAndWaitForRetryProcess(-1));
 
                 Assert.False(mockProvider.TryGetBlob(out _));
             }
@@ -630,7 +637,7 @@ protected override bool OnTryCreateBlob(byte[] buffer, out PersistentBlob blob)
             return blob.TryWrite(buffer);
         }
 
-        protected override bool OnTryGetBlob(out PersistentBlob blob)
+        protected override bool OnTryGetBlob([NotNullWhen(true)] out PersistentBlob? blob)
         {
             blob = this.GetBlobs().FirstOrDefault();
 
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests.csproj b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests.csproj
index ad60a2385a2..21b320de546 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests.csproj
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests.csproj
@@ -2,8 +2,6 @@
 
   <PropertyGroup>
     <TargetFrameworks>$(TargetFrameworksForTests)</TargetFrameworks>
-    <!-- this is temporary. will remove in future PR. -->
-    <Nullable>disable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpAttributeTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpAttributeTests.cs
index af31f32c795..a325874fb30 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpAttributeTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpAttributeTests.cs
@@ -1,6 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+using System.Diagnostics.CodeAnalysis;
 using Google.Protobuf.Collections;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation;
 using Xunit;
@@ -13,19 +14,19 @@ public class OtlpAttributeTests
     [Fact]
     public void NullValueAttribute()
     {
-        var kvp = new KeyValuePair<string, object>("key", null);
-        Assert.False(TryTransformTag(kvp, out var _));
+        var kvp = new KeyValuePair<string, object?>("key", null);
+        Assert.False(TryTransformTag(kvp, out _));
     }
 
     [Fact]
     public void EmptyArrays()
     {
-        var kvp = new KeyValuePair<string, object>("key", Array.Empty<int>());
+        var kvp = new KeyValuePair<string, object?>("key", Array.Empty<int>());
         Assert.True(TryTransformTag(kvp, out var attribute));
         Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.ArrayValue, attribute.Value.ValueCase);
         Assert.Empty(attribute.Value.ArrayValue.Values);
 
-        kvp = new KeyValuePair<string, object>("key", Array.Empty<object>());
+        kvp = new KeyValuePair<string, object?>("key", Array.Empty<object>());
         Assert.True(TryTransformTag(kvp, out attribute));
         Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.ArrayValue, attribute.Value.ValueCase);
         Assert.Empty(attribute.Value.ArrayValue.Values);
@@ -48,7 +49,7 @@ public void EmptyArrays()
     [InlineData(new long[] { 1, 2, 3 })]
     public void IntegralTypesSupported(object value)
     {
-        var kvp = new KeyValuePair<string, object>("key", value);
+        var kvp = new KeyValuePair<string, object?>("key", value);
         Assert.True(TryTransformTag(kvp, out var attribute));
 
         switch (value)
@@ -77,7 +78,7 @@ public void IntegralTypesSupported(object value)
     [InlineData(new double[] { 1, 2, 3 })]
     public void FloatingPointTypesSupported(object value)
     {
-        var kvp = new KeyValuePair<string, object>("key", value);
+        var kvp = new KeyValuePair<string, object?>("key", value);
         Assert.True(TryTransformTag(kvp, out var attribute));
 
         switch (value)
@@ -104,7 +105,7 @@ public void FloatingPointTypesSupported(object value)
     [InlineData(new bool[] { true, false, true })]
     public void BooleanTypeSupported(object value)
     {
-        var kvp = new KeyValuePair<string, object>("key", value);
+        var kvp = new KeyValuePair<string, object?>("key", value);
         Assert.True(TryTransformTag(kvp, out var attribute));
 
         switch (value)
@@ -131,7 +132,7 @@ public void BooleanTypeSupported(object value)
     [InlineData("string")]
     public void StringTypesSupported(object value)
     {
-        var kvp = new KeyValuePair<string, object>("key", value);
+        var kvp = new KeyValuePair<string, object?>("key", value);
         Assert.True(TryTransformTag(kvp, out var attribute));
         Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.StringValue, attribute.Value.ValueCase);
         Assert.Equal(Convert.ToString(value), attribute.Value.StringValue);
@@ -141,9 +142,9 @@ public void StringTypesSupported(object value)
     public void ObjectArrayTypesSupported()
     {
         var obj = new object();
-        var objectArray = new object[] { null, "a", 'b', true, int.MaxValue, long.MaxValue, float.MaxValue, double.MaxValue, obj };
+        var objectArray = new object?[] { null, "a", 'b', true, int.MaxValue, long.MaxValue, float.MaxValue, double.MaxValue, obj };
 
-        var kvp = new KeyValuePair<string, object>("key", objectArray);
+        var kvp = new KeyValuePair<string, object?>("key", objectArray);
 
         Assert.True(TryTransformTag(kvp, out var attribute));
         Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.ArrayValue, attribute.Value.ValueCase);
@@ -179,14 +180,14 @@ public void ObjectArrayTypesSupported()
     public void StringArrayTypesSupported()
     {
         var charArray = new char[] { 'a', 'b', 'c' };
-        var stringArray = new string[] { "a", "b", "c", string.Empty, null };
+        var stringArray = new string?[] { "a", "b", "c", string.Empty, null };
 
-        var kvp = new KeyValuePair<string, object>("key", charArray);
+        var kvp = new KeyValuePair<string, object?>("key", charArray);
         Assert.True(TryTransformTag(kvp, out var attribute));
         Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.ArrayValue, attribute.Value.ValueCase);
         Assert.Equal(charArray.Select(x => x.ToString()), attribute.Value.ArrayValue.Values.Select(x => x.StringValue));
 
-        kvp = new KeyValuePair<string, object>("key", stringArray);
+        kvp = new KeyValuePair<string, object?>("key", stringArray);
         Assert.True(TryTransformTag(kvp, out attribute));
         Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.ArrayValue, attribute.Value.ValueCase);
 
@@ -221,12 +222,12 @@ public void ToStringIsCalledForAllOtherTypes()
             new nint[] { 1, 2, 3 },
             new nuint[] { 1, 2, 3 },
             new decimal[] { 1, 2, 3 },
-            new object[] { new object[3], new object(), null },
+            new object?[] { new object[3], new object(), null },
         };
 
         foreach (var value in testValues)
         {
-            var kvp = new KeyValuePair<string, object>("key", value);
+            var kvp = new KeyValuePair<string, object?>("key", value);
             Assert.True(TryTransformTag(kvp, out var attribute));
             Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.StringValue, attribute.Value.ValueCase);
             Assert.Equal(value.ToString(), attribute.Value.StringValue);
@@ -234,11 +235,12 @@ public void ToStringIsCalledForAllOtherTypes()
 
         foreach (var value in testArrayValues)
         {
-            var kvp = new KeyValuePair<string, object>("key", value);
+            var kvp = new KeyValuePair<string, object?>("key", value);
             Assert.True(TryTransformTag(kvp, out var attribute));
             Assert.Equal(OtlpCommon.AnyValue.ValueOneofCase.ArrayValue, attribute.Value.ValueCase);
 
             var array = value as Array;
+            Assert.NotNull(array);
             for (var i = 0; i < attribute.Value.ArrayValue.Values.Count; ++i)
             {
                 var expectedValue = array.GetValue(i)?.ToString();
@@ -249,7 +251,7 @@ public void ToStringIsCalledForAllOtherTypes()
                 Assert.Equal(expectedValueCase, attribute.Value.ArrayValue.Values[i].ValueCase);
                 if (expectedValueCase != OtlpCommon.AnyValue.ValueOneofCase.None)
                 {
-                    Assert.Equal(array.GetValue(i).ToString(), attribute.Value.ArrayValue.Values[i].StringValue);
+                    Assert.Equal(array.GetValue(i)!.ToString(), attribute.Value.ArrayValue.Values[i].StringValue);
                 }
             }
         }
@@ -258,14 +260,14 @@ public void ToStringIsCalledForAllOtherTypes()
     [Fact]
     public void ExceptionInToStringIsCaught()
     {
-        var kvp = new KeyValuePair<string, object>("key", new MyToStringMethodThrowsAnException());
-        Assert.False(TryTransformTag(kvp, out var _));
+        var kvp = new KeyValuePair<string, object?>("key", new MyToStringMethodThrowsAnException());
+        Assert.False(TryTransformTag(kvp, out _));
 
-        kvp = new KeyValuePair<string, object>("key", new object[] { 1, false, new MyToStringMethodThrowsAnException() });
-        Assert.False(TryTransformTag(kvp, out var _));
+        kvp = new KeyValuePair<string, object?>("key", new object[] { 1, false, new MyToStringMethodThrowsAnException() });
+        Assert.False(TryTransformTag(kvp, out _));
     }
 
-    private static bool TryTransformTag(KeyValuePair<string, object> tag, out OtlpCommon.KeyValue attribute)
+    private static bool TryTransformTag(KeyValuePair<string, object?> tag, [NotNullWhen(true)] out OtlpCommon.KeyValue? attribute)
     {
         var destination = new RepeatedField<OtlpCommon.KeyValue>();
 
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsExtensionsTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsExtensionsTests.cs
index 2b7810dfadf..4018998b890 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsExtensionsTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsExtensionsTests.cs
@@ -73,7 +73,7 @@ public void GetMetadataFromHeadersThrowsExceptionOnInvalidFormat(string headers)
     [Theory]
     [InlineData("")]
     [InlineData(null)]
-    public void GetHeaders_NoOptionHeaders_ReturnsStandardHeaders(string optionHeaders)
+    public void GetHeaders_NoOptionHeaders_ReturnsStandardHeaders(string? optionHeaders)
     {
         var options = new OtlpExporterOptions
         {
@@ -158,19 +158,19 @@ public void AppendPathIfNotPresent_TracesPath_AppendsCorrectly(string inputUri,
     [InlineData(OtlpExportProtocol.Grpc, typeof(OtlpGrpcLogExportClient), false, 10000, "disk")]
     [InlineData(OtlpExportProtocol.HttpProtobuf, typeof(OtlpHttpLogExportClient), false, 10000, "disk")]
     [InlineData(OtlpExportProtocol.HttpProtobuf, typeof(OtlpHttpLogExportClient), true, 8000, "disk")]
-    public void GetTransmissionHandler_InitializesCorrectHandlerExportClientAndTimeoutValue(OtlpExportProtocol protocol, Type exportClientType, bool customHttpClient, int expectedTimeoutMilliseconds, string retryStrategy)
+    public void GetTransmissionHandler_InitializesCorrectHandlerExportClientAndTimeoutValue(OtlpExportProtocol protocol, Type exportClientType, bool customHttpClient, int expectedTimeoutMilliseconds, string? retryStrategy)
     {
         var exporterOptions = new OtlpExporterOptions() { Protocol = protocol };
         if (customHttpClient)
         {
             exporterOptions.HttpClientFactory = () =>
             {
-                return new HttpClient() { Timeout = TimeSpan.FromMilliseconds(expectedTimeoutMilliseconds) };
+                return new HttpClient { Timeout = TimeSpan.FromMilliseconds(expectedTimeoutMilliseconds) };
             };
         }
 
         var configuration = new ConfigurationBuilder()
-         .AddInMemoryCollection(new Dictionary<string, string> { [ExperimentalOptions.OtlpRetryEnvVar] = retryStrategy })
+         .AddInMemoryCollection(new Dictionary<string, string?> { [ExperimentalOptions.OtlpRetryEnvVar] = retryStrategy })
          .Build();
 
         if (exportClientType == typeof(OtlpGrpcTraceExportClient) || exportClientType == typeof(OtlpHttpTraceExportClient))
@@ -193,7 +193,7 @@ public void GetTransmissionHandler_InitializesCorrectHandlerExportClientAndTimeo
         }
     }
 
-    private static void AssertTransmissionHandler<T>(OtlpExporterTransmissionHandler<T> transmissionHandler, Type exportClientType, int expectedTimeoutMilliseconds, string retryStrategy)
+    private static void AssertTransmissionHandler<T>(OtlpExporterTransmissionHandler<T> transmissionHandler, Type exportClientType, int expectedTimeoutMilliseconds, string? retryStrategy)
     {
         if (retryStrategy == "in_memory")
         {
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs
index dc79c95c07b..c22f0e14863 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs
@@ -74,7 +74,7 @@ public void OtlpExporterOptions_UsingIConfiguration(object testDataObject)
     [Fact]
     public void OtlpExporterOptions_InvalidEnvironmentVariableOverride()
     {
-        var values = new Dictionary<string, string>()
+        var values = new Dictionary<string, string?>
         {
             ["EndpointWithInvalidValue"] = "invalid",
             ["TimeoutWithInvalidValue"] = "invalid",
@@ -104,7 +104,7 @@ public void OtlpExporterOptions_InvalidEnvironmentVariableOverride()
     [Fact]
     public void OtlpExporterOptions_SetterOverridesEnvironmentVariable()
     {
-        var values = new Dictionary<string, string>()
+        var values = new Dictionary<string, string?>
         {
             ["Endpoint"] = "http://test:8888",
             ["Timeout"] = "2000",
@@ -169,7 +169,7 @@ public void OtlpExporterOptions_SettingEndpointToNullResetsAppendSignalPathToEnd
     {
         var options = new OtlpExporterOptions(OtlpExporterOptionsConfigurationType.Default);
 
-        Assert.Throws<ArgumentNullException>(() => options.Endpoint = null);
+        Assert.Throws<ArgumentNullException>(() => options.Endpoint = null!);
     }
 
     [Fact]
@@ -177,7 +177,7 @@ public void OtlpExporterOptions_HttpClientFactoryThrowsWhenSetToNull()
     {
         var options = new OtlpExporterOptions(OtlpExporterOptionsConfigurationType.Default);
 
-        Assert.Throws<ArgumentNullException>(() => options.HttpClientFactory = null);
+        Assert.Throws<ArgumentNullException>(() => options.HttpClientFactory = null!);
     }
 
     [Fact]
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpLogExporterTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpLogExporterTests.cs
index f494a2683c6..c47fa7b5a5d 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpLogExporterTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpLogExporterTests.cs
@@ -7,7 +7,6 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Options;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation.Transmission;
 using OpenTelemetry.Internal;
@@ -100,7 +99,7 @@ public void UserHttpFactoryCalledWhenUsingHttpProtobuf()
             Assert.Equal(2, invocations);
         }
 
-        options.HttpClientFactory = () => null;
+        options.HttpClientFactory = () => null!;
         Assert.Throws<InvalidOperationException>(() =>
         {
             using var exporter = new OtlpLogExporter(options);
@@ -218,6 +217,7 @@ public void AddOtlpLogExporterParseStateValueCanBeTurnedOffHosting(bool parseSta
 
         var host = hostBuilder.Build();
         var loggerFactory = host.Services.GetService<ILoggerFactory>();
+        Assert.NotNull(loggerFactory);
         var logger = loggerFactory.CreateLogger("OtlpLogExporterTests");
         logger.Log(LogLevel.Information, default, new { propertyA = "valueA" }, null, (s, e) => "Custom state log message");
         Assert.Single(logRecords);
@@ -290,7 +290,7 @@ public void OtlpLogRecordTestWhenStateValuesArePopulated()
     [InlineData("true")]
     [InlineData("false")]
     [InlineData(null)]
-    public void CheckToOtlpLogRecordEventId(string emitLogEventAttributes)
+    public void CheckToOtlpLogRecordEventId(string? emitLogEventAttributes)
     {
         var logRecords = new List<LogRecord>();
         using var loggerFactory = LoggerFactory.Create(builder =>
@@ -309,7 +309,7 @@ public void CheckToOtlpLogRecordEventId(string emitLogEventAttributes)
         Assert.Single(logRecords);
 
         var configuration = new ConfigurationBuilder()
-          .AddInMemoryCollection(new Dictionary<string, string> { [ExperimentalOptions.EmitLogEventEnvVar] = emitLogEventAttributes })
+          .AddInMemoryCollection(new Dictionary<string, string?> { [ExperimentalOptions.EmitLogEventEnvVar] = emitLogEventAttributes })
           .Build();
 
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new(configuration));
@@ -375,6 +375,7 @@ public void CheckToOtlpLogRecordTimestamps()
         var logRecord = logRecords[0];
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
 
+        Assert.NotNull(otlpLogRecord);
         Assert.True(otlpLogRecord.TimeUnixNano > 0);
         Assert.True(otlpLogRecord.ObservedTimeUnixNano > 0);
     }
@@ -397,9 +398,10 @@ public void CheckToOtlpLogRecordTraceIdSpanIdFlagWithNoActivity()
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
 
         Assert.Null(Activity.Current);
+        Assert.NotNull(otlpLogRecord);
         Assert.True(otlpLogRecord.TraceId.IsEmpty);
         Assert.True(otlpLogRecord.SpanId.IsEmpty);
-        Assert.True(otlpLogRecord.Flags == 0);
+        Assert.Equal(0u, otlpLogRecord.Flags);
     }
 
     [Fact]
@@ -428,6 +430,7 @@ public void CheckToOtlpLogRecordSpanIdTraceIdAndFlag()
         var logRecord = logRecords[0];
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
 
+        Assert.NotNull(otlpLogRecord);
         Assert.Equal(expectedTraceId.ToString(), ActivityTraceId.CreateFromBytes(otlpLogRecord.TraceId.ToByteArray()).ToString());
         Assert.Equal(expectedSpanId.ToString(), ActivitySpanId.CreateFromBytes(otlpLogRecord.SpanId.ToByteArray()).ToString());
         Assert.Equal((uint)logRecord.TraceFlags, otlpLogRecord.Flags);
@@ -465,6 +468,7 @@ public void CheckToOtlpLogRecordSeverityLevelAndText(LogLevel logLevel)
 #pragma warning disable CS0618 // Type or member is obsolete
         Assert.Equal(logRecord.LogLevel.ToString(), otlpLogRecord.SeverityText);
 #pragma warning restore CS0618 // Type or member is obsolete
+        Assert.NotNull(logRecord.Severity);
         Assert.Equal((int)logRecord.Severity, (int)otlpLogRecord.SeverityNumber);
         switch (logLevel)
         {
@@ -546,7 +550,7 @@ public void CheckToOtlpLogRecordBodyIsPopulated(bool includeFormattedMessage)
 
         // Scenario 3 - Using the raw ILogger.Log Method, but with null
         // formatter.
-        logger.Log(LogLevel.Information, default, "state", exception: null, formatter: null);
+        logger.Log(LogLevel.Information, default, "state", exception: null, formatter: null!);
         Assert.Single(logRecords);
 
         logRecord = logRecords[0];
@@ -590,6 +594,7 @@ public void LogRecordBodyIsExportedWhenUsingBridgeApi(bool isBodySet)
 
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecords[0]);
 
+        Assert.NotNull(otlpLogRecord);
         if (isBodySet)
         {
             Assert.Equal("Hello world", otlpLogRecord.Body?.StringValue);
@@ -601,6 +606,7 @@ public void LogRecordBodyIsExportedWhenUsingBridgeApi(bool isBodySet)
 
         otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecords[1]);
 
+        Assert.NotNull(otlpLogRecord);
         Assert.Equal(2, otlpLogRecord.Attributes.Count);
 
         var index = 0;
@@ -638,6 +644,7 @@ public void CheckToOtlpLogRecordExceptionAttributes()
         var otlpLogRecordAttributes = otlpLogRecord.Attributes.ToString();
 
         Assert.Contains(SemanticConventions.AttributeExceptionType, otlpLogRecordAttributes);
+        Assert.NotNull(logRecord.Exception);
         Assert.Contains(logRecord.Exception.GetType().Name, otlpLogRecordAttributes);
 
         Assert.Contains(SemanticConventions.AttributeExceptionMessage, otlpLogRecordAttributes);
@@ -785,6 +792,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsFalse_DoesNotContainScopeAttribu
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         var actualScope = TryGetAttribute(otlpLogRecord, expectedScopeKey);
         Assert.Null(actualScope);
     }
@@ -819,6 +827,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeStrin
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -857,6 +866,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeBoolV
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -907,6 +917,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeIntVa
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -935,7 +946,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeDoubl
         // Act.
         using (logger.BeginScope(new List<KeyValuePair<string, object>>
         {
-            new KeyValuePair<string, object>(scopeKey, scopeValue),
+            new(scopeKey, scopeValue),
         }))
         {
             logger.LogInformation("Some log information message.");
@@ -945,6 +956,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeDoubl
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -973,7 +985,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeDoubl
         // Act.
         using (logger.BeginScope(new List<KeyValuePair<string, object>>
         {
-            new KeyValuePair<string, object>(scopeKey, scopeValue),
+            new(scopeKey, scopeValue),
         }))
         {
             logger.LogInformation("Some log information message.");
@@ -983,6 +995,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_ContainsScopeAttributeDoubl
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -1038,6 +1051,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndScopeStateIsOfPrimitiveT
         var logger = loggerFactory.CreateLogger(nameof(OtlpLogExporterTests));
 
         var scopeState = Activator.CreateInstance(typeOfScopeState);
+        Assert.NotNull(scopeState);
 
         // Act.
         using (logger.BeginScope(scopeState))
@@ -1080,6 +1094,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndScopeStateIsOfDictionary
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -1105,10 +1120,11 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndScopeStateIsOfEnumerable
 
         const string scopeKey = "Some scope key";
         const string scopeValue = "Some scope value";
-        var scopeValues = new List<KeyValuePair<string, object>> { new KeyValuePair<string, object>(scopeKey, scopeValue) };
+        var scopeValues = new List<KeyValuePair<string, object?>> { new(scopeKey, scopeValue) };
         var scopeState = Activator.CreateInstance(typeOfScopeState, scopeValues) as ICollection<KeyValuePair<string, object>>;
 
         // Act.
+        Assert.NotNull(scopeState);
         using (logger.BeginScope(scopeState))
         {
             logger.LogInformation("Some log information message.");
@@ -1118,6 +1134,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndScopeStateIsOfEnumerable
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         Assert.Single(otlpLogRecord.Attributes);
         var actualScope = TryGetAttribute(otlpLogRecord, scopeKey);
         Assert.NotNull(actualScope);
@@ -1157,6 +1174,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndMultipleScopesAreAdded_C
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         var allScopeValues = otlpLogRecord.Attributes
             .Where(_ => _.Key == scopeKey1 || _.Key == scopeKey2)
             .Select(_ => _.Value.StringValue);
@@ -1197,6 +1215,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndMultipleScopeLevelsAreAd
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         var allScopeValues = otlpLogRecord.Attributes
             .Where(_ => _.Key == scopeKey1 || _.Key == scopeKey2)
             .Select(_ => _.Value.StringValue);
@@ -1242,6 +1261,7 @@ public void ToOtlpLog_WhenOptionsIncludeScopesIsTrue_AndScopeIsUsedInLogMethod_C
         var logRecord = logRecords.Single();
         var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
         var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecord);
+        Assert.NotNull(otlpLogRecord);
         var allScopeValues = otlpLogRecord.Attributes
             .Where(_ => _.Key == scopeKey1 || _.Key == scopeKey2)
             .Select(_ => _.Value.StringValue);
@@ -1314,9 +1334,9 @@ public void AddOtlpLogExporterLogRecordProcessorOptionsTest(ExportProcessorType
         }
         else
         {
-            var simpleProcesor = processor as SimpleLogRecordExportProcessor;
+            var simpleProcessor = processor as SimpleLogRecordExportProcessor;
 
-            Assert.NotNull(simpleProcesor);
+            Assert.NotNull(simpleProcessor);
         }
     }
 
@@ -1381,7 +1401,7 @@ public void ValidateInstrumentationScope()
     [InlineData("logging", false)]
     [InlineData(null, true)]
     [InlineData("logging", true)]
-    public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggerFactoryCreate(string optionsName, bool callUseOpenTelemetry)
+    public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggerFactoryCreate(string? optionsName, bool callUseOpenTelemetry)
     {
         RunVerifyEnvironmentVariablesTakenFromIConfigurationTest(
             optionsName,
@@ -1406,7 +1426,7 @@ public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggerFact
     [InlineData("logging", false)]
     [InlineData(null, true)]
     [InlineData("logging", true)]
-    public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggingBuilder(string optionsName, bool callUseOpenTelemetry)
+    public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggingBuilder(string? optionsName, bool callUseOpenTelemetry)
     {
         RunVerifyEnvironmentVariablesTakenFromIConfigurationTest(
             optionsName,
@@ -1433,7 +1453,7 @@ public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggingBui
     [Theory]
     [InlineData("my_instrumentation_scope_name", "my_instrumentation_scope_name")]
     [InlineData(null, "")]
-    public void LogRecordLoggerNameIsExportedWhenUsingBridgeApi(string loggerName, string expectedScopeName)
+    public void LogRecordLoggerNameIsExportedWhenUsingBridgeApi(string? loggerName, string expectedScopeName)
     {
         LogRecordAttributeList attributes = default;
         attributes.Add("name", "tomato");
@@ -1469,10 +1489,10 @@ public void LogRecordLoggerNameIsExportedWhenUsingBridgeApi(string loggerName, s
     }
 
     private static void RunVerifyEnvironmentVariablesTakenFromIConfigurationTest(
-        string optionsName,
+        string? optionsName,
         Func<Action<IServiceCollection>, (IDisposable Container, ILoggerFactory LoggerFactory)> createLoggerFactoryFunc)
     {
-        var values = new Dictionary<string, string>()
+        var values = new Dictionary<string, string?>
         {
             [OtlpSpecConfigDefinitions.DefaultEndpointEnvVarName] = "http://test:8888",
         };
@@ -1542,7 +1562,7 @@ private static void RunVerifyEnvironmentVariablesTakenFromIConfigurationTest(
         Assert.True(allConfigureDelegateCalled);
     }
 
-    private static OtlpCommon.KeyValue TryGetAttribute(OtlpLogs.LogRecord record, string key)
+    private static OtlpCommon.KeyValue? TryGetAttribute(OtlpLogs.LogRecord record, string key)
     {
         return record.Attributes.FirstOrDefault(att => att.Key == key);
     }
@@ -1550,11 +1570,11 @@ private static OtlpCommon.KeyValue TryGetAttribute(OtlpLogs.LogRecord record, st
     private static void ConfigureOtlpExporter(
         ILoggingBuilder builder,
         bool callUseOpenTelemetry,
-        string name = null,
-        Action<OtlpExporterOptions> configureExporter = null,
-        Action<OtlpExporterOptions, LogRecordExportProcessorOptions> configureExporterAndProcessor = null,
-        Action<OpenTelemetryLoggerOptions> configureOptions = null,
-        List<LogRecord> logRecords = null)
+        string? name = null,
+        Action<OtlpExporterOptions>? configureExporter = null,
+        Action<OtlpExporterOptions, LogRecordExportProcessorOptions>? configureExporterAndProcessor = null,
+        Action<OpenTelemetryLoggerOptions>? configureOptions = null,
+        List<LogRecord>? logRecords = null)
     {
         if (callUseOpenTelemetry)
         {
@@ -1604,23 +1624,4 @@ private static void ConfigureOtlpExporter(
 #pragma warning restore CS0618 // Type or member is obsolete
         }
     }
-
-    private sealed class TestOptionsMonitor<T> : IOptionsMonitor<T>
-    {
-        private readonly T instance;
-
-        public TestOptionsMonitor(T instance)
-        {
-            this.instance = instance;
-        }
-
-        public T CurrentValue => this.instance;
-
-        public T Get(string name) => this.instance;
-
-        public IDisposable OnChange(Action<T, string> listener)
-        {
-            throw new NotImplementedException();
-        }
-    }
 }
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMetricsExporterTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMetricsExporterTests.cs
index 07124e63a85..d92f33ee6a9 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMetricsExporterTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMetricsExporterTests.cs
@@ -21,10 +21,10 @@ namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 [Collection("EnvVars")]
 public class OtlpMetricsExporterTests : IDisposable
 {
-    private static readonly KeyValuePair<string, object>[] KeyValues = new KeyValuePair<string, object>[]
+    private static readonly KeyValuePair<string, object?>[] KeyValues = new KeyValuePair<string, object?>[]
     {
-        new KeyValuePair<string, object>("key1", "value1"),
-        new KeyValuePair<string, object>("key2", 123),
+        new("key1", "value1"),
+        new("key2", 123),
     };
 
     public OtlpMetricsExporterTests()
@@ -57,14 +57,14 @@ void CheckMetricReaderDefaults()
 
             var metricReader = typeof(MetricReader)
                 .Assembly
-                .GetType("OpenTelemetry.Metrics.MeterProviderSdk")
-                .GetField("reader", bindingFlags)
+                .GetType("OpenTelemetry.Metrics.MeterProviderSdk")?
+                .GetField("reader", bindingFlags)?
                 .GetValue(meterProvider) as PeriodicExportingMetricReader;
 
             Assert.NotNull(metricReader);
 
-            var exportIntervalMilliseconds = (int)typeof(PeriodicExportingMetricReader)
-                .GetField("ExportIntervalMilliseconds", bindingFlags)
+            var exportIntervalMilliseconds = (int?)typeof(PeriodicExportingMetricReader)?
+                .GetField("ExportIntervalMilliseconds", bindingFlags)?
                 .GetValue(metricReader);
 
             Assert.Equal(60000, exportIntervalMilliseconds);
@@ -129,8 +129,8 @@ public void UserHttpFactoryCalled()
             Assert.Equal(2, invocations);
         }
 
-        options.HttpClientFactory = () => null;
-        Assert.Throws<InvalidOperationException>(() =>
+        options.HttpClientFactory = () => throw new NotSupportedException();
+        Assert.Throws<NotSupportedException>(() =>
         {
             using var exporter = new OtlpMetricExporter(options);
         });
@@ -219,7 +219,7 @@ public void ToOtlpResourceMetricsTest(bool includeServiceNameInResource)
     [InlineData("test_gauge", null, null, 123L, null, true)]
     [InlineData("test_gauge", null, null, null, 123.45, true)]
     [InlineData("test_gauge", "description", "unit", 123L, null)]
-    public void TestGaugeToOtlpMetric(string name, string description, string unit, long? longValue, double? doubleValue, bool enableExemplars = false)
+    public void TestGaugeToOtlpMetric(string name, string? description, string? unit, long? longValue, double? doubleValue, bool enableExemplars = false)
     {
         var metrics = new List<Metric>();
 
@@ -236,7 +236,7 @@ public void TestGaugeToOtlpMetric(string name, string description, string unit,
         }
         else
         {
-            meter.CreateObservableGauge(name, () => doubleValue.Value, unit, description);
+            meter.CreateObservableGauge(name, () => doubleValue!.Value, unit, description);
         }
 
         provider.ForceFlush();
@@ -294,7 +294,7 @@ public void TestGaugeToOtlpMetric(string name, string description, string unit,
     [InlineData("test_counter", null, null, null, 123.45, MetricReaderTemporalityPreference.Delta, false, true)]
     [InlineData("test_counter", "description", "unit", 123L, null, MetricReaderTemporalityPreference.Cumulative)]
     [InlineData("test_counter", null, null, 123L, null, MetricReaderTemporalityPreference.Delta, true)]
-    public void TestCounterToOtlpMetric(string name, string description, string unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
+    public void TestCounterToOtlpMetric(string name, string? description, string? unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
     {
         var metrics = new List<Metric>();
 
@@ -308,7 +308,7 @@ public void TestCounterToOtlpMetric(string name, string description, string unit
             })
             .Build();
 
-        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object>>();
+        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object?>>();
         if (longValue.HasValue)
         {
             var counter = meter.CreateCounter<long>(name, unit, description);
@@ -317,7 +317,7 @@ public void TestCounterToOtlpMetric(string name, string description, string unit
         else
         {
             var counter = meter.CreateCounter<double>(name, unit, description);
-            counter.Add(doubleValue.Value, attributes);
+            counter.Add(doubleValue!.Value, attributes);
         }
 
         provider.ForceFlush();
@@ -391,7 +391,7 @@ public void TestCounterToOtlpMetric(string name, string description, string unit
     [InlineData("test_counter", null, null, null, -123.45, MetricReaderTemporalityPreference.Delta, false, true)]
     [InlineData("test_counter", "description", "unit", 123L, null, MetricReaderTemporalityPreference.Cumulative)]
     [InlineData("test_counter", null, null, 123L, null, MetricReaderTemporalityPreference.Delta, true)]
-    public void TestUpDownCounterToOtlpMetric(string name, string description, string unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
+    public void TestUpDownCounterToOtlpMetric(string name, string? description, string? unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
     {
         var metrics = new List<Metric>();
 
@@ -405,7 +405,7 @@ public void TestUpDownCounterToOtlpMetric(string name, string description, strin
             })
             .Build();
 
-        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object>>();
+        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object?>>();
         if (longValue.HasValue)
         {
             var counter = meter.CreateUpDownCounter<long>(name, unit, description);
@@ -414,7 +414,7 @@ public void TestUpDownCounterToOtlpMetric(string name, string description, strin
         else
         {
             var counter = meter.CreateUpDownCounter<double>(name, unit, description);
-            counter.Add(doubleValue.Value, attributes);
+            counter.Add(doubleValue!.Value, attributes);
         }
 
         provider.ForceFlush();
@@ -488,7 +488,7 @@ public void TestUpDownCounterToOtlpMetric(string name, string description, strin
     [InlineData("test_histogram", null, null, null, 123.45, MetricReaderTemporalityPreference.Delta, false, true)]
     [InlineData("test_histogram", "description", "unit", 123L, null, MetricReaderTemporalityPreference.Cumulative)]
     [InlineData("test_histogram", null, null, 123L, null, MetricReaderTemporalityPreference.Delta, true)]
-    public void TestExponentialHistogramToOtlpMetric(string name, string description, string unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
+    public void TestExponentialHistogramToOtlpMetric(string name, string? description, string? unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
     {
         var metrics = new List<Metric>();
 
@@ -506,7 +506,7 @@ public void TestExponentialHistogramToOtlpMetric(string name, string description
             })
             .Build();
 
-        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object>>();
+        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object?>>();
         if (longValue.HasValue)
         {
             var histogram = meter.CreateHistogram<long>(name, unit, description);
@@ -516,7 +516,7 @@ public void TestExponentialHistogramToOtlpMetric(string name, string description
         else
         {
             var histogram = meter.CreateHistogram<double>(name, unit, description);
-            histogram.Record(doubleValue.Value, attributes);
+            histogram.Record(doubleValue!.Value, attributes);
             histogram.Record(0, attributes);
         }
 
@@ -577,7 +577,7 @@ public void TestExponentialHistogramToOtlpMetric(string name, string description
             {
                 Assert.Equal(0, dataPoint.Sum);
                 Assert.Null(dataPoint.Negative);
-                Assert.True(dataPoint.Positive.Offset == 0);
+                Assert.Equal(0, dataPoint.Positive.Offset);
                 Assert.Empty(dataPoint.Positive.BucketCounts);
             }
         }
@@ -594,7 +594,7 @@ public void TestExponentialHistogramToOtlpMetric(string name, string description
             {
                 Assert.Equal(0, dataPoint.Sum);
                 Assert.Null(dataPoint.Negative);
-                Assert.True(dataPoint.Positive.Offset == 0);
+                Assert.Equal(0, dataPoint.Positive.Offset);
                 Assert.Empty(dataPoint.Positive.BucketCounts);
             }
         }
@@ -628,7 +628,7 @@ public void TestExponentialHistogramToOtlpMetric(string name, string description
     [InlineData("test_histogram", null, null, null, 123.45, MetricReaderTemporalityPreference.Delta, false, true)]
     [InlineData("test_histogram", "description", "unit", 123L, null, MetricReaderTemporalityPreference.Cumulative)]
     [InlineData("test_histogram", null, null, 123L, null, MetricReaderTemporalityPreference.Delta, true)]
-    public void TestHistogramToOtlpMetric(string name, string description, string unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
+    public void TestHistogramToOtlpMetric(string name, string? description, string? unit, long? longValue, double? doubleValue, MetricReaderTemporalityPreference aggregationTemporality, bool enableKeyValues = false, bool enableExemplars = false)
     {
         var metrics = new List<Metric>();
 
@@ -642,7 +642,7 @@ public void TestHistogramToOtlpMetric(string name, string description, string un
             })
             .Build();
 
-        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object>>();
+        var attributes = enableKeyValues ? KeyValues : Array.Empty<KeyValuePair<string, object?>>();
         if (longValue.HasValue)
         {
             var histogram = meter.CreateHistogram<long>(name, unit, description);
@@ -651,7 +651,7 @@ public void TestHistogramToOtlpMetric(string name, string description, string un
         else
         {
             var histogram = meter.CreateHistogram<double>(name, unit, description);
-            histogram.Record(doubleValue.Value, attributes);
+            histogram.Record(doubleValue!.Value, attributes);
         }
 
         provider.ForceFlush();
@@ -732,7 +732,7 @@ public void TestTemporalityPreferenceUsingConfiguration(string configValue, Metr
     {
         var testExecuted = false;
 
-        var configData = new Dictionary<string, string> { [OtlpSpecConfigDefinitionTests.MetricsData.TemporalityKeyName] = configValue };
+        var configData = new Dictionary<string, string?> { [OtlpSpecConfigDefinitionTests.MetricsData.TemporalityKeyName] = configValue };
         var configuration = new ConfigurationBuilder()
             .AddInMemoryCollection(configData)
             .Build();
@@ -786,9 +786,9 @@ public void TestTemporalityPreferenceUsingEnvVar(string configValue, MetricReade
     [InlineData(true, true)]
     public void ToOtlpExemplarTests(bool enableTagFiltering, bool enableTracing)
     {
-        ActivitySource activitySource = null;
-        Activity activity = null;
-        TracerProvider tracerProvider = null;
+        ActivitySource? activitySource = null;
+        Activity? activity = null;
+        TracerProvider? tracerProvider = null;
 
         using var meter = new Meter(Utils.GetCurrentMethodName());
 
@@ -823,8 +823,8 @@ public void ToOtlpExemplarTests(bool enableTagFiltering, bool enableTracing)
         var counterDouble = meter.CreateCounter<double>("testCounterDouble");
         var counterLong = meter.CreateCounter<long>("testCounterLong");
 
-        counterDouble.Add(1.18D, new KeyValuePair<string, object>("key1", "value1"));
-        counterLong.Add(18L, new KeyValuePair<string, object>("key1", "value1"));
+        counterDouble.Add(1.18D, new KeyValuePair<string, object?>("key1", "value1"));
+        counterLong.Add(18L, new KeyValuePair<string, object?>("key1", "value1"));
 
         meterProvider.ForceFlush();
 
@@ -869,6 +869,7 @@ void AssertExemplars<T>(T value, Metric metric)
             else
             {
                 byte[] traceIdBytes = new byte[16];
+                Assert.NotNull(activity);
                 activity.TraceId.CopyTo(traceIdBytes);
 
                 byte[] spanIdBytes = new byte[8];
@@ -914,7 +915,7 @@ public void Dispose()
         GC.SuppressFinalize(this);
     }
 
-    private static void VerifyExemplars<T>(long? longValue, double? doubleValue, bool enableExemplars, Func<T, OtlpMetrics.Exemplar> getExemplarFunc, T state)
+    private static void VerifyExemplars<T>(long? longValue, double? doubleValue, bool enableExemplars, Func<T, OtlpMetrics.Exemplar?> getExemplarFunc, T state)
     {
         var exemplar = getExemplarFunc(state);
 
@@ -928,6 +929,7 @@ private static void VerifyExemplars<T>(long? longValue, double? doubleValue, boo
             }
             else
             {
+                Assert.NotNull(doubleValue);
                 Assert.Equal(doubleValue.Value, exemplar.AsDouble);
             }
         }
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTestHelpers.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTestHelpers.cs
index ec9dbbe4312..7cc6b10336e 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTestHelpers.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTestHelpers.cs
@@ -11,7 +11,7 @@ namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 internal static class OtlpTestHelpers
 {
     public static void AssertOtlpAttributes(
-        IEnumerable<KeyValuePair<string, object>> expected,
+        IEnumerable<KeyValuePair<string, object?>> expected,
         RepeatedField<OtlpCommon.KeyValue> actual)
     {
         var expectedAttributes = expected.ToList();
@@ -20,6 +20,7 @@ public static void AssertOtlpAttributes(
         {
             var current = expectedAttributes[i].Value;
             Assert.Equal(expectedAttributes[i].Key, actual[i].Key);
+            Assert.NotNull(current);
 
             if (current.GetType().IsArray)
             {
@@ -91,7 +92,7 @@ public static void AssertOtlpAttributes(
         Assert.Equal(expectedSize, actual.Count);
     }
 
-    private static void AssertOtlpAttributeValue(object expected, OtlpCommon.AnyValue actual)
+    private static void AssertOtlpAttributeValue(object? expected, OtlpCommon.AnyValue actual)
     {
         switch (expected)
         {
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs
index 18434043bc7..84d3076500a 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs
@@ -63,8 +63,8 @@ public void AddOtlpTraceExporterNamedOptionsSupported()
     [Fact]
     public void OtlpExporter_BadArgs()
     {
-        TracerProviderBuilder builder = null;
-        Assert.Throws<ArgumentNullException>(() => builder.AddOtlpExporter());
+        TracerProviderBuilder? builder = null;
+        Assert.Throws<ArgumentNullException>(() => builder!.AddOtlpExporter());
     }
 
     [Fact]
@@ -98,7 +98,7 @@ public void UserHttpFactoryCalled()
             Assert.Equal(2, invocations);
         }
 
-        options.HttpClientFactory = () => null;
+        options.HttpClientFactory = () => null!;
         Assert.Throws<InvalidOperationException>(() =>
         {
             using var exporter = new OtlpTraceExporter(options);
@@ -131,8 +131,8 @@ public void ServiceProviderHttpClientFactoryInvoked()
     [InlineData(false)]
     public void ToOtlpResourceSpansTest(bool includeServiceNameInResource)
     {
-        var evenTags = new[] { new KeyValuePair<string, object>("k0", "v0") };
-        var oddTags = new[] { new KeyValuePair<string, object>("k1", "v1") };
+        var evenTags = new[] { new KeyValuePair<string, object?>("k0", "v0") };
+        var oddTags = new[] { new KeyValuePair<string, object?>("k1", "v1") };
         var sources = new[]
         {
             new ActivitySource("even", "2.4.6"),
@@ -163,7 +163,7 @@ public void ToOtlpResourceSpansTest(bool includeServiceNameInResource)
             var activityKind = isEven ? ActivityKind.Client : ActivityKind.Server;
             var activityTags = isEven ? evenTags : oddTags;
 
-            using Activity activity = source.StartActivity($"span-{i}", activityKind, parentContext: default, activityTags);
+            using Activity? activity = source.StartActivity($"span-{i}", activityKind, parentContext: default, activityTags);
         }
 
         Assert.Equal(10, exportedItems.Count);
@@ -232,12 +232,12 @@ public void SpanLimitsTest()
             SpanLinkCountLimit = 1,
         };
 
-        var tags = new ActivityTagsCollection()
+        var tags = new ActivityTagsCollection
         {
-            new KeyValuePair<string, object>("TruncatedTag", "12345"),
-            new KeyValuePair<string, object>("TruncatedStringArray", new string[] { "12345", "1234", string.Empty, null }),
-            new KeyValuePair<string, object>("TruncatedObjectTag", new object()),
-            new KeyValuePair<string, object>("OneTagTooMany", 1),
+            new("TruncatedTag", "12345"),
+            new("TruncatedStringArray", new string?[] { "12345", "1234", string.Empty, null }),
+            new("TruncatedObjectTag", new object()),
+            new("OneTagTooMany", 1),
         };
 
         var links = new[]
@@ -249,6 +249,8 @@ public void SpanLimitsTest()
         using var activitySource = new ActivitySource(nameof(this.SpanLimitsTest));
         using var activity = activitySource.StartActivity("root", ActivityKind.Server, default(ActivityContext), tags, links);
 
+        Assert.NotNull(activity);
+
         var event1 = new ActivityEvent("Event", DateTime.UtcNow, tags);
         var event2 = new ActivityEvent("OneEventTooMany", DateTime.Now, tags);
 
@@ -262,7 +264,7 @@ public void SpanLimitsTest()
         Assert.Equal(1u, otlpSpan.DroppedAttributesCount);
         Assert.Equal("1234", otlpSpan.Attributes[0].Value.StringValue);
         ArrayValueAsserts(otlpSpan.Attributes[1].Value.ArrayValue.Values);
-        Assert.Equal(new object().ToString().Substring(0, 4), otlpSpan.Attributes[2].Value.StringValue);
+        Assert.Equal(new object().ToString()!.Substring(0, 4), otlpSpan.Attributes[2].Value.StringValue);
 
         Assert.Single(otlpSpan.Events);
         Assert.Equal(1u, otlpSpan.DroppedEventsCount);
@@ -270,7 +272,7 @@ public void SpanLimitsTest()
         Assert.Equal(1u, otlpSpan.Events[0].DroppedAttributesCount);
         Assert.Equal("1234", otlpSpan.Events[0].Attributes[0].Value.StringValue);
         ArrayValueAsserts(otlpSpan.Events[0].Attributes[1].Value.ArrayValue.Values);
-        Assert.Equal(new object().ToString().Substring(0, 4), otlpSpan.Events[0].Attributes[2].Value.StringValue);
+        Assert.Equal(new object().ToString()!.Substring(0, 4), otlpSpan.Events[0].Attributes[2].Value.StringValue);
 
         Assert.Single(otlpSpan.Links);
         Assert.Equal(1u, otlpSpan.DroppedLinksCount);
@@ -278,11 +280,11 @@ public void SpanLimitsTest()
         Assert.Equal(1u, otlpSpan.Links[0].DroppedAttributesCount);
         Assert.Equal("1234", otlpSpan.Links[0].Attributes[0].Value.StringValue);
         ArrayValueAsserts(otlpSpan.Links[0].Attributes[1].Value.ArrayValue.Values);
-        Assert.Equal(new object().ToString().Substring(0, 4), otlpSpan.Links[0].Attributes[2].Value.StringValue);
+        Assert.Equal(new object().ToString()!.Substring(0, 4), otlpSpan.Links[0].Attributes[2].Value.StringValue);
 
         void ArrayValueAsserts(RepeatedField<OtlpCommon.AnyValue> values)
         {
-            var expectedStringArray = new string[] { "1234", "1234", string.Empty, null };
+            var expectedStringArray = new string?[] { "1234", "1234", string.Empty, null };
             for (var i = 0; i < expectedStringArray.Length; ++i)
             {
                 var expectedValue = expectedStringArray[i];
@@ -307,21 +309,22 @@ public void ToOtlpSpanTest()
 
         using var rootActivity = activitySource.StartActivity("root", ActivityKind.Producer);
 
-        var attributes = new List<KeyValuePair<string, object>>
-        {
-            new KeyValuePair<string, object>("bool", true),
-            new KeyValuePair<string, object>("long", 1L),
-            new KeyValuePair<string, object>("string", "text"),
-            new KeyValuePair<string, object>("double", 3.14),
-            new KeyValuePair<string, object>("int", 1),
-            new KeyValuePair<string, object>("datetime", DateTime.UtcNow),
-            new KeyValuePair<string, object>("bool_array", new bool[] { true, false }),
-            new KeyValuePair<string, object>("int_array", new int[] { 1, 2 }),
-            new KeyValuePair<string, object>("double_array", new double[] { 1.0, 2.09 }),
-            new KeyValuePair<string, object>("string_array", new string[] { "a", "b" }),
-            new KeyValuePair<string, object>("datetime_array", new DateTime[] { DateTime.UtcNow, DateTime.Now }),
+        var attributes = new List<KeyValuePair<string, object?>>
+        {
+            new("bool", true),
+            new("long", 1L),
+            new("string", "text"),
+            new("double", 3.14),
+            new("int", 1),
+            new("datetime", DateTime.UtcNow),
+            new("bool_array", new bool[] { true, false }),
+            new("int_array", new int[] { 1, 2 }),
+            new("double_array", new double[] { 1.0, 2.09 }),
+            new("string_array", new string[] { "a", "b" }),
+            new("datetime_array", new DateTime[] { DateTime.UtcNow, DateTime.Now }),
         };
 
+        Assert.NotNull(rootActivity);
         foreach (var kvp in attributes)
         {
             rootActivity.SetTag(kvp.Key, kvp.Value);
@@ -359,16 +362,17 @@ public void ToOtlpSpanTest()
         var expectedEndTimeUnixNano = expectedStartTimeUnixNano + (duration.TotalMilliseconds * 1_000_000);
         Assert.Equal(expectedEndTimeUnixNano, otlpSpan.EndTimeUnixNano);
 
-        var childLinks = new List<ActivityLink> { new ActivityLink(rootActivity.Context, new ActivityTagsCollection(attributes)) };
+        var childLinks = new List<ActivityLink> { new(rootActivity.Context, new ActivityTagsCollection(attributes)) };
         var childActivity = activitySource.StartActivity(
             "child",
             ActivityKind.Client,
             rootActivity.Context,
             links: childLinks);
 
+        Assert.NotNull(childActivity);
         childActivity.SetStatus(Status.Error);
 
-        var childEvents = new List<ActivityEvent> { new ActivityEvent("e0"), new ActivityEvent("e1", default, new ActivityTagsCollection(attributes)) };
+        var childEvents = new List<ActivityEvent> { new("e0"), new("e1", default, new ActivityTagsCollection(attributes)) };
         childActivity.AddEvent(childEvents[0]);
         childActivity.AddEvent(childEvents[1]);
 
@@ -400,7 +404,9 @@ public void ToOtlpSpanTest()
         Assert.Equal(childLinks.Count, otlpSpan.Links.Count);
         for (var i = 0; i < childLinks.Count; i++)
         {
-            OtlpTestHelpers.AssertOtlpAttributes(childLinks[i].Tags.ToList(), otlpSpan.Links[i].Attributes);
+            var tags = childLinks[i].Tags;
+            Assert.NotNull(tags);
+            OtlpTestHelpers.AssertOtlpAttributes(tags, otlpSpan.Links[i].Attributes);
         }
 
         var flags = (OtlpTrace.SpanFlags)otlpSpan.Flags;
@@ -416,7 +422,7 @@ public void ToOtlpSpanActivitiesWithNullArrayTest()
         using var rootActivity = activitySource.StartActivity("root", ActivityKind.Client);
         Assert.NotNull(rootActivity);
 
-        var stringArr = new string[] { "test", string.Empty, null };
+        var stringArr = new string?[] { "test", string.Empty, null };
         rootActivity.SetTag("stringArray", stringArr);
 
         var otlpSpan = rootActivity.ToOtlpSpan(DefaultSdkLimitOptions);
@@ -439,10 +445,11 @@ public void ToOtlpSpanNativeActivityStatusTest(ActivityStatusCode expectedStatus
     {
         using var activitySource = new ActivitySource(nameof(this.ToOtlpSpanTest));
         using var activity = activitySource.StartActivity("Name");
+        Assert.NotNull(activity);
         activity.SetStatus(expectedStatusCode, statusDescription);
 
         var otlpSpan = activity.ToOtlpSpan(DefaultSdkLimitOptions);
-
+        Assert.NotNull(otlpSpan);
         if (expectedStatusCode == ActivityStatusCode.Unset)
         {
             Assert.Null(otlpSpan.Status);
@@ -471,11 +478,13 @@ public void ToOtlpSpanStatusTagTest(StatusCode expectedStatusCode, string status
     {
         using var activitySource = new ActivitySource(nameof(this.ToOtlpSpanTest));
         using var activity = activitySource.StartActivity("Name");
+        Assert.NotNull(activity);
         activity.SetTag(SpanAttributeConstants.StatusCodeKey, statusCodeTagValue);
         activity.SetTag(SpanAttributeConstants.StatusDescriptionKey, statusDescription);
 
         var otlpSpan = activity.ToOtlpSpan(DefaultSdkLimitOptions);
 
+        Assert.NotNull(otlpSpan);
         Assert.NotNull(otlpSpan.Status);
         Assert.Equal((int)expectedStatusCode, (int)otlpSpan.Status.Code);
 
@@ -497,10 +506,12 @@ public void ToOtlpSpanStatusTagIsCaseInsensitiveTest(StatusCode expectedStatusCo
     {
         using var activitySource = new ActivitySource(nameof(this.ToOtlpSpanTest));
         using var activity = activitySource.StartActivity("Name");
+        Assert.NotNull(activity);
         activity.SetTag(SpanAttributeConstants.StatusCodeKey, statusCodeTagValue);
 
         var otlpSpan = activity.ToOtlpSpan(DefaultSdkLimitOptions);
 
+        Assert.NotNull(otlpSpan);
         Assert.NotNull(otlpSpan.Status);
         Assert.Equal((int)expectedStatusCode, (int)otlpSpan.Status.Code);
     }
@@ -510,13 +521,15 @@ public void ToOtlpSpanActivityStatusTakesPrecedenceOverStatusTagsWhenActivitySta
     {
         using var activitySource = new ActivitySource(nameof(this.ToOtlpSpanTest));
         using var activity = activitySource.StartActivity("Name");
-        const string TagDescriptionOnError = "Description when TagStatusCode is Error.";
+        const string tagDescriptionOnError = "Description when TagStatusCode is Error.";
+        Assert.NotNull(activity);
         activity.SetStatus(ActivityStatusCode.Ok);
         activity.SetTag(SpanAttributeConstants.StatusCodeKey, "ERROR");
-        activity.SetTag(SpanAttributeConstants.StatusDescriptionKey, TagDescriptionOnError);
+        activity.SetTag(SpanAttributeConstants.StatusDescriptionKey, tagDescriptionOnError);
 
         var otlpSpan = activity.ToOtlpSpan(DefaultSdkLimitOptions);
 
+        Assert.NotNull(otlpSpan);
         Assert.NotNull(otlpSpan.Status);
         Assert.Equal((int)ActivityStatusCode.Ok, (int)otlpSpan.Status.Code);
         Assert.Empty(otlpSpan.Status.Message);
@@ -527,15 +540,17 @@ public void ToOtlpSpanActivityStatusTakesPrecedenceOverStatusTagsWhenActivitySta
     {
         using var activitySource = new ActivitySource(nameof(this.ToOtlpSpanTest));
         using var activity = activitySource.StartActivity("Name");
-        const string StatusDescriptionOnError = "Description when ActivityStatusCode is Error.";
-        activity.SetStatus(ActivityStatusCode.Error, StatusDescriptionOnError);
+        const string statusDescriptionOnError = "Description when ActivityStatusCode is Error.";
+        Assert.NotNull(activity);
+        activity.SetStatus(ActivityStatusCode.Error, statusDescriptionOnError);
         activity.SetTag(SpanAttributeConstants.StatusCodeKey, "OK");
 
         var otlpSpan = activity.ToOtlpSpan(DefaultSdkLimitOptions);
 
+        Assert.NotNull(otlpSpan);
         Assert.NotNull(otlpSpan.Status);
         Assert.Equal((int)ActivityStatusCode.Error, (int)otlpSpan.Status.Code);
-        Assert.Equal(StatusDescriptionOnError, otlpSpan.Status.Message);
+        Assert.Equal(statusDescriptionOnError, otlpSpan.Status.Message);
     }
 
     [Theory]
@@ -545,6 +560,7 @@ public void ToOtlpSpanTraceStateTest(bool traceStateWasSet)
     {
         using var activitySource = new ActivitySource(nameof(this.ToOtlpSpanTest));
         using var activity = activitySource.StartActivity("Name");
+        Assert.NotNull(activity);
         string tracestate = "a=b;c=d";
         if (traceStateWasSet)
         {
@@ -552,6 +568,7 @@ public void ToOtlpSpanTraceStateTest(bool traceStateWasSet)
         }
 
         var otlpSpan = activity.ToOtlpSpan(DefaultSdkLimitOptions);
+        Assert.NotNull(otlpSpan);
 
         if (traceStateWasSet)
         {
@@ -571,6 +588,7 @@ public void ToOtlpSpanPeerServiceTest()
 
         using var rootActivity = activitySource.StartActivity("root", ActivityKind.Client);
 
+        Assert.NotNull(rootActivity);
         rootActivity.SetTag(SemanticConventions.AttributeHttpHost, "opentelemetry.io");
 
         var otlpSpan = rootActivity.ToOtlpSpan(DefaultSdkLimitOptions);
@@ -641,7 +659,7 @@ public void Null_BatchExportProcessorOptions_SupportedTest()
                 {
                     o.Protocol = OtlpExportProtocol.HttpProtobuf;
                     o.ExportProcessorType = ExportProcessorType.Batch;
-                    o.BatchExportProcessorOptions = null;
+                    o.BatchExportProcessorOptions = null!;
                 });
     }
 
@@ -650,8 +668,8 @@ public void NonnamedOptionsMutateSharedInstanceTest()
     {
         var testOptionsInstance = new OtlpExporterOptions();
 
-        OtlpExporterOptions tracerOptions = null;
-        OtlpExporterOptions meterOptions = null;
+        OtlpExporterOptions? tracerOptions = null;
+        OtlpExporterOptions? meterOptions = null;
 
         var services = new ServiceCollection();
 
@@ -695,8 +713,8 @@ public void NonnamedOptionsMutateSharedInstanceTest()
     [Fact]
     public void NamedOptionsMutateSeparateInstancesTest()
     {
-        OtlpExporterOptions tracerOptions = null;
-        OtlpExporterOptions meterOptions = null;
+        OtlpExporterOptions? tracerOptions = null;
+        OtlpExporterOptions? meterOptions = null;
 
         var services = new ServiceCollection();
 
@@ -753,9 +771,11 @@ public void SpanFlagsTest(bool isRecorded, bool isRemote)
             isRemote: isRemote);
 
         using var rootActivity = activitySource.StartActivity("root", ActivityKind.Server, ctx);
+        Assert.NotNull(rootActivity);
 
         var otlpSpan = rootActivity.ToOtlpSpan(DefaultSdkLimitOptions);
 
+        Assert.NotNull(otlpSpan);
         var flags = (OtlpTrace.SpanFlags)otlpSpan.Flags;
 
         ActivityTraceFlags traceFlags = (ActivityTraceFlags)(flags & OtlpTrace.SpanFlags.TraceFlagsMask);
@@ -802,9 +822,11 @@ public void SpanLinkFlagsTest(bool isRecorded, bool isRemote)
         };
 
         using var rootActivity = activitySource.StartActivity("root", ActivityKind.Server, default(ActivityContext), links: links);
+        Assert.NotNull(rootActivity);
 
         var otlpSpan = rootActivity.ToOtlpSpan(DefaultSdkLimitOptions);
 
+        Assert.NotNull(otlpSpan);
         var spanLink = Assert.Single(otlpSpan.Links);
 
         var flags = (OtlpTrace.SpanFlags)spanLink.Flags;
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/SdkLimitOptionsTests.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/SdkLimitOptionsTests.cs
index dc36def4665..0a737ff1438 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/SdkLimitOptionsTests.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/SdkLimitOptionsTests.cs
@@ -135,7 +135,7 @@ public void SpanAttributeCountLimitFallback()
     [Fact]
     public void SdkLimitOptionsUsingIConfiguration()
     {
-        var values = new Dictionary<string, string>
+        var values = new Dictionary<string, string?>
         {
             ["OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT"] = "23",
             ["OTEL_ATTRIBUTE_COUNT_LIMIT"] = "24",
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestExportClient.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestExportClient.cs
index eab9178db49..bbecfa2fa37 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestExportClient.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestExportClient.cs
@@ -32,7 +32,7 @@ public bool Shutdown(int timeoutMilliseconds)
 
     private class TestExportClientResponse : ExportClientResponse
     {
-        public TestExportClientResponse(bool success, DateTime deadline, Exception exception)
+        public TestExportClientResponse(bool success, DateTime deadline, Exception? exception)
             : base(success, deadline, exception)
         {
         }
diff --git a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestHttpMessageHandler.cs b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestHttpMessageHandler.cs
index cf62af4e994..2e5d6ede2b0 100644
--- a/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestHttpMessageHandler.cs
+++ b/test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/TestHttpMessageHandler.cs
@@ -9,14 +9,14 @@ namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 
 internal class TestHttpMessageHandler : HttpMessageHandler
 {
-    public HttpRequestMessage HttpRequestMessage { get; private set; }
+    public HttpRequestMessage? HttpRequestMessage { get; private set; }
 
-    public byte[] HttpRequestContent { get; private set; }
+    public byte[]? HttpRequestContent { get; private set; }
 
     public virtual HttpResponseMessage InternalSend(HttpRequestMessage request, CancellationToken cancellationToken)
     {
         this.HttpRequestMessage = request;
-        this.HttpRequestContent = request.Content.ReadAsByteArrayAsync().Result;
+        this.HttpRequestContent = request.Content!.ReadAsByteArrayAsync().Result;
         return new HttpResponseMessage();
     }
 
diff --git a/test/OpenTelemetry.Tests/Shared/EventSourceTestHelper.cs b/test/OpenTelemetry.Tests/Shared/EventSourceTestHelper.cs
index c0f5055d490..26d82bb6a0b 100644
--- a/test/OpenTelemetry.Tests/Shared/EventSourceTestHelper.cs
+++ b/test/OpenTelemetry.Tests/Shared/EventSourceTestHelper.cs
@@ -1,6 +1,8 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#nullable enable
+
 using System.Diagnostics.Tracing;
 using System.Globalization;
 using System.Reflection;
@@ -26,7 +28,7 @@ private static void VerifyMethodImplementation(EventSource eventSource, MethodIn
             object[] eventArguments = GenerateEventArguments(eventMethod);
             eventMethod.Invoke(eventSource, eventArguments);
 
-            EventWrittenEventArgs actualEvent = listener.Messages.FirstOrDefault(x => x.EventName == eventMethod.Name);
+            EventWrittenEventArgs? actualEvent = listener.Messages.FirstOrDefault(x => x.EventName == eventMethod.Name);
 
             if (actualEvent == null)
             {
@@ -47,7 +49,7 @@ private static void VerifyMethodImplementation(EventSource eventSource, MethodIn
         }
         catch (Exception e)
         {
-            var name = eventMethod.DeclaringType.Name + "." + eventMethod.Name;
+            var name = eventMethod.DeclaringType?.Name + "." + eventMethod.Name;
 
             throw new Exception("Method '" + name + "' is implemented incorrectly.", e);
         }
@@ -78,7 +80,7 @@ private static object GenerateArgument(ParameterInfo parameter)
 
         if (parameter.ParameterType.IsValueType)
         {
-            return Activator.CreateInstance(parameter.ParameterType);
+            return Activator.CreateInstance(parameter.ParameterType)!;
         }
 
         throw new NotSupportedException("Complex types are not supported");
@@ -99,13 +101,14 @@ private static void VerifyEventLevel(MethodInfo eventMethod, EventWrittenEventAr
     private static void VerifyEventMessage(MethodInfo eventMethod, EventWrittenEventArgs actualEvent, object[] eventArguments)
     {
         string expectedMessage = eventArguments.Length == 0
-            ? GetEventAttribute(eventMethod).Message
-            : string.Format(CultureInfo.InvariantCulture, GetEventAttribute(eventMethod).Message, eventArguments);
-        string actualMessage = string.Format(CultureInfo.InvariantCulture, actualEvent.Message, actualEvent.Payload.ToArray());
+            ? GetEventAttribute(eventMethod).Message!
+            : string.Format(CultureInfo.InvariantCulture, GetEventAttribute(eventMethod).Message!, eventArguments)!;
+        string actualMessage = string.Format(CultureInfo.InvariantCulture, actualEvent.Message!, actualEvent.Payload!.ToArray());
         AssertEqual(nameof(VerifyEventMessage), expectedMessage, actualMessage);
     }
 
     private static void AssertEqual<T>(string methodName, T expected, T actual)
+        where T : notnull
     {
         if (!expected.Equals(actual))
         {
diff --git a/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundFactAttribute.cs b/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundFactAttribute.cs
index adfebcaf184..0fb748ba2c2 100644
--- a/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundFactAttribute.cs
+++ b/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundFactAttribute.cs
@@ -1,6 +1,8 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#nullable enable
+
 using Xunit;
 
 namespace OpenTelemetry.Tests;
@@ -15,9 +17,9 @@ public SkipUnlessEnvVarFoundFactAttribute(string environmentVariable)
         }
     }
 
-    public static string GetEnvironmentVariable(string environmentVariableName)
+    public static string? GetEnvironmentVariable(string environmentVariableName)
     {
-        string environmentVariableValue = Environment.GetEnvironmentVariable(environmentVariableName, EnvironmentVariableTarget.Process);
+        string? environmentVariableValue = Environment.GetEnvironmentVariable(environmentVariableName, EnvironmentVariableTarget.Process);
 
         if (string.IsNullOrEmpty(environmentVariableValue))
         {
diff --git a/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundTheoryAttribute.cs b/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundTheoryAttribute.cs
index dc5ce2ca66f..056c37036dc 100644
--- a/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundTheoryAttribute.cs
+++ b/test/OpenTelemetry.Tests/Shared/SkipUnlessEnvVarFoundTheoryAttribute.cs
@@ -1,6 +1,8 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#nullable enable
+
 using Xunit;
 
 namespace OpenTelemetry.Tests;
@@ -15,9 +17,9 @@ public SkipUnlessEnvVarFoundTheoryAttribute(string environmentVariable)
         }
     }
 
-    public static string GetEnvironmentVariable(string environmentVariableName)
+    public static string? GetEnvironmentVariable(string environmentVariableName)
     {
-        string environmentVariableValue = Environment.GetEnvironmentVariable(environmentVariableName, EnvironmentVariableTarget.Process);
+        string? environmentVariableValue = Environment.GetEnvironmentVariable(environmentVariableName, EnvironmentVariableTarget.Process);
 
         if (string.IsNullOrEmpty(environmentVariableValue))
         {
diff --git a/test/OpenTelemetry.Tests/Shared/TestActivityProcessor.cs b/test/OpenTelemetry.Tests/Shared/TestActivityProcessor.cs
index 36d47b7b8fa..a386b67c8d3 100644
--- a/test/OpenTelemetry.Tests/Shared/TestActivityProcessor.cs
+++ b/test/OpenTelemetry.Tests/Shared/TestActivityProcessor.cs
@@ -1,14 +1,16 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#nullable enable
+
 using System.Diagnostics;
 
 namespace OpenTelemetry.Tests;
 
 internal class TestActivityProcessor : BaseProcessor<Activity>
 {
-    public Action<Activity> StartAction;
-    public Action<Activity> EndAction;
+    public Action<Activity>? StartAction;
+    public Action<Activity>? EndAction;
 
     public TestActivityProcessor()
     {
diff --git a/test/OpenTelemetry.Tests/Shared/TestEventListener.cs b/test/OpenTelemetry.Tests/Shared/TestEventListener.cs
index b0cf1d0b120..4e9d79c4735 100644
--- a/test/OpenTelemetry.Tests/Shared/TestEventListener.cs
+++ b/test/OpenTelemetry.Tests/Shared/TestEventListener.cs
@@ -1,6 +1,8 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#nullable enable
+
 using System.Diagnostics.Tracing;
 
 namespace OpenTelemetry.Tests;
@@ -39,7 +41,7 @@ public TestEventListener()
     }
 
     /// <summary>Gets or sets the handler for event source creation.</summary>
-    public Action<EventSource> OnOnEventSourceCreated { get; set; }
+    public Action<EventSource>? OnOnEventSourceCreated { get; set; }
 
     /// <summary>Gets or sets the handler for event source writes.</summary>
     public Action<EventWrittenEventArgs> OnOnEventWritten { get; set; }
@@ -81,7 +83,7 @@ protected override void OnEventWritten(EventWrittenEventArgs eventData)
     protected override void OnEventSourceCreated(EventSource eventSource)
     {
         // Check for null because this method is called by the base class constructor before we can initialize it
-        Action<EventSource> callback = this.OnOnEventSourceCreated;
+        Action<EventSource>? callback = this.OnOnEventSourceCreated;
         callback?.Invoke(eventSource);
     }
 }