Fix more nullability warnings after updating to net6.0

Author: drewnoakes

src/NetMQ.Tests/ExceptionTests.cs

@@ -108,6 +108,7 @@ private static T Clone<T>(T source) where T : class
             return Deserialise<T>(Serialise(source));
         }
 
+#pragma warning disable SYSLIB0011 // BinaryFormatter is obsolete
         private static Stream Serialise(object source)
         {
             var formatter = new BinaryFormatter();
@@ -122,6 +123,7 @@ private static T Deserialise<T>(Stream stream)
             stream.Position = 0;
             return (T)formatter.Deserialize(stream);
         }
+#pragma warning restore SYSLIB0011 // BinaryFormatter is obsolete
 
         #endregion
     }

src/NetMQ.Tests/NetMQ.Tests.csproj

@@ -42,8 +42,8 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
     <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
-    <PackageReference Include="xunit" Version="2.4.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1" />
+    <PackageReference Include="xunit" Version="2.4.2-pre.13" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net47' ">

src/NetMQ.Tests/OutgoingSocketExtensionsTests.cs

@@ -213,6 +213,7 @@ public void SendFrameEmpty()
             var socket = new MockOutgoingSocket((ref Msg msg, TimeSpan timeout, bool more) =>
             {
                 Assert.Equal(SendReceiveConstants.InfiniteTimeout, timeout);
+                Assert.NotNull(msg.UnsafeData);
                 Assert.Empty(msg.UnsafeData);
                 Assert.False(more);
                 return true;
@@ -227,6 +228,7 @@ public void SendMoreFrameEmpty()
             var socket = new MockOutgoingSocket((ref Msg msg, TimeSpan timeout, bool more) =>
             {
                 Assert.Equal(SendReceiveConstants.InfiniteTimeout, timeout);
+                Assert.NotNull(msg.UnsafeData);
                 Assert.Empty(msg.UnsafeData);
                 Assert.True(more);
                 return true;
@@ -242,6 +244,7 @@ public void TrySendFrameEmpty()
             var socket = new MockOutgoingSocket((ref Msg msg, TimeSpan timeout, bool more) =>
             {
                 Assert.Equal(TimeSpan.Zero, timeout);
+                Assert.NotNull(msg.UnsafeData);
                 Assert.Empty(msg.UnsafeData);
                 Assert.False(more);
                 return true;
@@ -257,6 +260,7 @@ public void TrySendFrameEmptyFailed()
             var socket = new MockOutgoingSocket((ref Msg msg, TimeSpan timeout, bool more) =>
             {
                 Assert.Equal(TimeSpan.Zero, timeout);
+                Assert.NotNull(msg.UnsafeData);
                 Assert.Empty(msg.UnsafeData);
                 Assert.False(more);
                 return false;

src/NetMQ.Tests/PgmTests.cs

@@ -82,7 +82,7 @@ public void UseInterface()
         {
             var hostEntry = Dns.GetHostEntry(Dns.GetHostName());
 
-            string ip = hostEntry.AddressList
+            string? ip = hostEntry.AddressList
                 .Where(addr => addr.AddressFamily == AddressFamily.InterNetwork)
                 .Select(addr => addr.ToString())
                 .FirstOrDefault();

src/NetMQ.Tests/ThrowingTraceListener.cs

@@ -6,16 +6,16 @@ namespace NetMQ.Tests
 {
     public sealed class ThrowingTraceListener : TraceListener
     {
-        public override void Fail(string message, string detailMessage)
+        public override void Fail(string? message, string? detailMessage)
         {
             throw new DebugAssertFailureException((message + Environment.NewLine + detailMessage).Trim());
         }
 
-        public override void Write(string message)
+        public override void Write(string? message)
         {
         }
 
-        public override void WriteLine(string message)
+        public override void WriteLine(string? message)
         {
         }