diff --git a/src/csharp/Grpc.Core.Tests/Internal/DefaultSerializationContextTest.cs b/src/csharp/Grpc.Core.Tests/Internal/DefaultSerializationContextTest.cs
new file mode 100644
index 00000000000..4d09d80bb72
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/Internal/DefaultSerializationContextTest.cs
@@ -0,0 +1,144 @@
+#region Copyright notice and license
+
+// Copyright 2019 The gRPC Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#endregion
+
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Internal.Tests
+{
+    public class DefaultSerializationContextTest
+    {
+        [TestCase]
+        public void CompleteAllowedOnlyOnce()
+        {
+            var context = new DefaultSerializationContext();
+            var buffer = GetTestBuffer(10);
+
+            context.Complete(buffer);
+            Assert.Throws(typeof(InvalidOperationException), () => context.Complete(buffer));
+            Assert.Throws(typeof(InvalidOperationException), () => context.Complete());
+        }
+
+        [TestCase]
+        public void CompleteAllowedOnlyOnce2()
+        {
+            var context = new DefaultSerializationContext();
+
+            context.Complete();
+            Assert.Throws(typeof(InvalidOperationException), () => context.Complete(GetTestBuffer(10)));
+            Assert.Throws(typeof(InvalidOperationException), () => context.Complete());
+        }
+
+        [TestCase(0)]
+        [TestCase(1)]
+        [TestCase(10)]
+        [TestCase(100)]
+        [TestCase(1000)]
+        public void ByteArrayPayload(int payloadSize)
+        {
+            var context = new DefaultSerializationContext();
+            var origPayload = GetTestBuffer(payloadSize);
+
+            context.Complete(origPayload);
+
+            var nativePayload = context.GetPayload().ToByteArray();
+            CollectionAssert.AreEqual(origPayload, nativePayload);
+        }
+
+        [TestCase(0)]
+        [TestCase(1)]
+        [TestCase(10)]
+        [TestCase(100)]
+        [TestCase(1000)]
+        public void BufferWriter_OneSegment(int payloadSize)
+        {
+            var context = new DefaultSerializationContext();
+            var origPayload = GetTestBuffer(payloadSize);
+
+            var bufferWriter = context.GetBufferWriter();
+            origPayload.AsSpan().CopyTo(bufferWriter.GetSpan(payloadSize));
+            bufferWriter.Advance(payloadSize);
+            // TODO: test that call to Complete() is required.
+
+            var nativePayload = context.GetPayload().ToByteArray();
+            CollectionAssert.AreEqual(origPayload, nativePayload);
+        }
+
+        [TestCase(1, 4)]  // small slice size tests grpc_slice with inline data
+        [TestCase(10, 4)]
+        [TestCase(100, 4)]
+        [TestCase(1000, 4)]
+        [TestCase(1, 64)]  // larger slice size tests allocated grpc_slices
+        [TestCase(10, 64)]
+        [TestCase(1000, 50)]
+        [TestCase(1000, 64)]
+        public void BufferWriter_MultipleSegments(int payloadSize, int maxSliceSize)
+        {
+            var context = new DefaultSerializationContext();
+            var origPayload = GetTestBuffer(payloadSize);
+
+            var bufferWriter = context.GetBufferWriter();
+            for (int offset = 0; offset < payloadSize; offset += maxSliceSize)
+            {
+                var sliceSize = Math.Min(maxSliceSize, payloadSize - offset);
+                // we allocate last slice as too big intentionally to test that shrinking works
+                var dest = bufferWriter.GetSpan(maxSliceSize);
+                
+                origPayload.AsSpan(offset, sliceSize).CopyTo(dest);
+                bufferWriter.Advance(sliceSize);
+            }
+            context.Complete();
+            
+            var nativePayload = context.GetPayload().ToByteArray();
+            CollectionAssert.AreEqual(origPayload, nativePayload);
+
+            context.GetPayload().Dispose(); // TODO: do it better.. (use the scope...)
+        }
+
+        // AdjustTailSpace(0) if previous tail size is 0....
+
+        // test that context.Complete() call is required...
+
+        // BufferWriter.GetMemory... (add refs to the original memory?)
+
+        // TODO: set payload and then get IBufferWriter should throw?
+
+        // TODO: test Reset()...
+
+        // TODO: destroy SliceBufferSafeHandles... (use usagescope...)
+
+
+
+
+        private byte[] GetTestBuffer(int length)
+        {
+            var testBuffer = new byte[length];
+            for (int i = 0; i < testBuffer.Length; i++)
+            {
+                testBuffer[i] = (byte) i;
+            }
+            return testBuffer;
+        }
+    }
+}
diff --git a/src/csharp/tests.json b/src/csharp/tests.json
index 2eb786e0983..75bda4c25ea 100644
--- a/src/csharp/tests.json
+++ b/src/csharp/tests.json
@@ -9,6 +9,7 @@
     "Grpc.Core.Internal.Tests.CompletionQueueSafeHandleTest",
     "Grpc.Core.Internal.Tests.DefaultDeserializationContextTest",
     "Grpc.Core.Internal.Tests.DefaultObjectPoolTest",
+    "Grpc.Core.Internal.Tests.DefaultSerializationContextTest",
     "Grpc.Core.Internal.Tests.FakeBufferReaderManagerTest",
     "Grpc.Core.Internal.Tests.MetadataArraySafeHandleTest",
     "Grpc.Core.Internal.Tests.ReusableSliceBufferTest",