add tests

Author: twsouthwick

src/Services/SessionState/BinarySessionSerializer.cs

@@ -162,10 +162,7 @@ public BinaryReaderSerializedSessionState(BinaryReader reader, ISessionKeySerial
 
                 if (serializer.TryDeserialize(key, bytes, out var result))
                 {
-                    if (result is not null)
-                    {
-                        this[key] = result;
-                    }
+                    this[key] = result;
                 }
                 else
                 {

test/Microsoft.AspNetCore.SystemWebAdapters.CoreServices.Tests/SessionState/Serialization/BinarySessionSerializerTests.cs

@@ -286,6 +286,33 @@ public async Task Serialize1KeyNull()
         Assert.Equal(ms.ToArray(), new byte[] { 2, 2, 105, 100, 0, 0, 0, 0, 1, 4, 107, 101, 121, 49, 1, 0, 0 });
     }
 
+    [Fact]
+    public async Task Deserialize1KeyNull()
+    {
+        // Arrange
+        var data = new byte[] { 2, 2, 105, 100, 0, 0, 0, 0, 1, 4, 107, 101, 121, 49, 1, 0, 0 };
+        var obj = new object();
+        var value = new byte[] { 0 };
+
+        var keySerializer = new Mock<ISessionKeySerializer>();
+        keySerializer.Setup(k => k.TryDeserialize("key1", value, out obj)).Returns(true);
+
+        var serializer = CreateSerializer(keySerializer.Object);
+
+        // Act
+        var result = await serializer.DeserializeAsync(new MemoryStream(data), default);
+
+        // Assert
+        Assert.Equal("id", result!.SessionID);
+        Assert.False(result.IsReadOnly);
+        Assert.False(result.IsAbandoned);
+        Assert.False(result.IsNewSession);
+        Assert.Equal(0, result.Timeout);
+        Assert.Equal(1, result.Count);
+        Assert.Same(obj, result["key1"]);
+        Assert.Collection(result.Keys, k => Assert.Equal("key1", k));
+    }
+
     [Fact]
     public async Task Deserialize1KeyV1()
     {