diff --git a/kx.Benchmark.Test/kx.Benchmark.Test.csproj b/kx.Benchmark.Test/kx.Benchmark.Test.csproj
index 2f9a120..d5d49b3 100644
--- a/kx.Benchmark.Test/kx.Benchmark.Test.csproj
+++ b/kx.Benchmark.Test/kx.Benchmark.Test.csproj
@@ -21,8 +21,6 @@
   <ItemGroup>
     <PackageReference Include="BenchmarkDotNet" Version="0.15.8" />
     <PackageReference Include="NUnit" Version="3.12.0" />
-    <PackageReference Include="NUnit3TestAdapter" Version="3.16.1" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.5.0" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/kx.Test/Connection/ConnectionSerialisationTests.cs b/kx.Test/Connection/ConnectionSerialisationTests.cs
index b8655bc..199a727 100644
--- a/kx.Test/Connection/ConnectionSerialisationTests.cs
+++ b/kx.Test/Connection/ConnectionSerialisationTests.cs
@@ -9,6 +9,8 @@ namespace kx.Test.Connection
     [TestFixture]
     public class ConnectionSerialisationTests
     {
+        private static readonly string[] Keys = {"Key_1"};
+        private static readonly object[] Values = {"Value_1"};
         private readonly int _testVersionNumber = 3;
 
         [Test]
@@ -402,7 +404,7 @@ public void ConnectionSerialisesAndDeserialisesTimeSpanInput()
         [Test]
         public void ConnectionSerialisesAndDeserialisesDictInput()
         {
-            c.Dict expected = new c.Dict(new string[] { "Key_1" }, new object[] { "Value_1" });
+            c.Dict expected = new c.Dict(Keys, Values);
 
             using (var connection = new c(_testVersionNumber))
             {
@@ -419,7 +421,7 @@ public void ConnectionSerialisesAndDeserialisesDictInput()
         [Test]
         public void ConnectionSerialisesAndDeserialisesFlipInput()
         {
-            c.Flip expected = new c.Flip(new c.Dict(new string[] { "Key_1" }, new object[] { "Value_1" }));
+            c.Flip expected = new c.Flip(new c.Dict(Keys, Values));
 
             using (var connection = new c(_testVersionNumber))
             {
diff --git a/kx.Test/Connection/ConnectionTests.cs b/kx.Test/Connection/ConnectionTests.cs
index 6a41a5a..57b8f66 100644
--- a/kx.Test/Connection/ConnectionTests.cs
+++ b/kx.Test/Connection/ConnectionTests.cs
@@ -1,4 +1,7 @@
 using System;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
 using kx.Test.TestUtils;
 using NUnit.Framework;
 
@@ -86,5 +89,156 @@ public void ConnectionThrowsSerialisableExpectionIfAuthenticationDoesNotPass()
                 Assert.IsNotNull(error);
             }
         }
+
+        [Test]
+        public void ProtectedConstructorAndBufferStateAreAccessibleToDerivedTypes()
+        {
+            using (var connection = new TestConnection())
+            {
+                Assert.IsNull(connection.ExposedReadBuffer);
+                Assert.IsFalse(connection.ExposedIsLittleEndian);
+                Assert.AreEqual(0, connection.ExposedReadPosition);
+
+                connection.ExposedReadPosition = 3;
+                Assert.AreEqual(3, connection.ExposedReadPosition);
+                Assert.Throws<ArgumentOutOfRangeException>(() => connection.ExposedReadPosition = -1);
+            }
+        }
+
+        [Test]
+        public void DisposeCanBeCalledMoreThanOnce()
+        {
+            var connection = new c(new MemoryStream());
+
+            connection.Dispose();
+
+            Assert.DoesNotThrow(connection.Dispose);
+        }
+
+        [Test]
+        public void CloseClosesBothStreamAndSocket()
+        {
+            using (var server = new TestableTcpServer())
+            {
+                var connection = new c("localhost", server.TestPort);
+
+                Assert.DoesNotThrow(connection.Close);
+                connection.Dispose();
+            }
+        }
+
+        [Test]
+        public void ExplicitTlsOptionsConstructorAcceptsNullAsDisabled()
+        {
+            using (var server = new TestableTcpServer())
+            using (var connection = new c("localhost", server.TestPort, Environment.UserName, 1024, null))
+            {
+                Assert.IsNotNull(connection);
+            }
+        }
+
+        [Test]
+        public async Task ParameterlessAsyncReadReturnsDeserialisedObject()
+        {
+            const int expected = 42;
+            byte[] message;
+            using (var serializer = new c(3))
+            {
+                message = serializer.Serialize(1, expected);
+            }
+
+            using (var stream = new MemoryStream(message))
+            using (var connection = new c(stream))
+            {
+                Assert.AreEqual(expected, await connection.kAsync());
+            }
+        }
+
+        [Test]
+        public async Task ParameterlessAsyncHeaderReadPopulatesReadableBuffer()
+        {
+            const int expected = 42;
+            byte[] message;
+            using (var serializer = new c(3))
+            {
+                message = serializer.Serialize(1, expected);
+            }
+
+            using (var stream = new MemoryStream(message))
+            using (var connection = new TestConnection(stream))
+            {
+                await connection.k0Async();
+
+                Assert.AreEqual(expected, connection.ExposedReadObject());
+            }
+        }
+
+        [TestCase(1)]
+        [TestCase(2)]
+        public async Task ParameterlessAsyncMessageWritesExpectedMessageType(int messageType)
+        {
+            const string expected = "payload";
+            using (var stream = new MemoryStream())
+            using (var connection = new c(stream))
+            {
+                if (messageType == 1)
+                {
+                    await connection.knAsync(expected);
+                }
+                else
+                {
+                    await connection.krAsync(expected);
+                }
+
+                byte[] message = stream.ToArray();
+                Assert.AreEqual(messageType, message[1]);
+                Assert.AreEqual(expected, connection.Deserialize(message));
+            }
+        }
+
+        [Test]
+        public async Task ProtectedParameterlessWriteAsyncWritesRequestedBytes()
+        {
+            byte[] expected = { 1, 2, 3, 4 };
+            using (var stream = new MemoryStream())
+            using (var connection = new TestConnection(stream))
+            {
+                await connection.ExposedWriteAsync(expected, expected.Length);
+
+                Assert.IsTrue(expected.SequenceEqual(stream.ToArray()));
+            }
+        }
+
+        private sealed class TestConnection : c
+        {
+            internal TestConnection()
+            {
+            }
+
+            internal TestConnection(Stream stream)
+                : base(stream)
+            {
+            }
+
+            internal byte[] ExposedReadBuffer => ReadBuffer;
+
+            internal int ExposedReadPosition
+            {
+                get => ReadPosition;
+                set => ReadPosition = value;
+            }
+
+            internal bool ExposedIsLittleEndian => IsLittleEndian;
+
+            internal object ExposedReadObject()
+            {
+                return ReadObject();
+            }
+
+            internal Task ExposedWriteAsync(byte[] bytes, int number)
+            {
+                return WriteAsync(bytes, number);
+            }
+        }
     }
 }
diff --git a/kx.Test/Connection/KExceptionTests.cs b/kx.Test/Connection/KExceptionTests.cs
new file mode 100644
index 0000000..d2f5c30
--- /dev/null
+++ b/kx.Test/Connection/KExceptionTests.cs
@@ -0,0 +1,40 @@
+using System;
+using NUnit.Framework;
+
+namespace kx.Test.Connection
+{
+    [TestFixture]
+    public class KExceptionTests
+    {
+        [Test]
+        public void DefaultConstructorCreatesExceptionWithDefaultMessage()
+        {
+            var exception = new KException();
+
+            Assert.IsNull(exception.InnerException);
+            Assert.IsNotEmpty(exception.Message);
+        }
+
+        [Test]
+        public void MessageConstructorPreservesMessage()
+        {
+            const string expected = "kdb error";
+
+            var exception = new KException(expected);
+
+            Assert.AreEqual(expected, exception.Message);
+        }
+
+        [Test]
+        public void InnerExceptionConstructorPreservesMessageAndCause()
+        {
+            const string expected = "serialization failed";
+            var cause = new InvalidOperationException("cause");
+
+            var exception = new KException(expected, cause);
+
+            Assert.AreEqual(expected, exception.Message);
+            Assert.AreSame(cause, exception.InnerException);
+        }
+    }
+}
diff --git a/kx/c.cs b/kx/c.cs
index a8db7a8..ddb47d1 100644
--- a/kx/c.cs
+++ b/kx/c.cs
@@ -369,6 +369,7 @@ public c(
         /// </remarks>
         protected c()
         {
+            _maxBufferSize = DefaultMaxBufferSize;
             _versionNumber = 3;
         }
 
@@ -382,6 +383,7 @@ protected c()
         /// </remarks>
         internal c(int versionNumber)
         {
+            _maxBufferSize = DefaultMaxBufferSize;
             _versionNumber = versionNumber;
         }
 
@@ -411,6 +413,7 @@ internal c(Stream clientStream)
         internal c(Stream clientStream, int versionNumber)
         {
             _clientStream = clientStream;
+            _maxBufferSize = DefaultMaxBufferSize;
             _versionNumber = versionNumber;
         }