* Added some unit tests for SqlLogEventWriter

* Added wrappers for SqlClientClasses to increase testablility (SqlConnectionWrapper, SqlCommandWrapper).

Author: ckadluba

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/ISqlCommandWrapper.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Data;
+using System.Data.Common;
+
+namespace Serilog.Sinks.MSSqlServer.Sinks.MSSqlServer.Platform
+{
+    internal interface ISqlCommandWrapper : IDisposable
+    {
+        CommandType CommandType { get; set; }
+        DbParameterCollection Parameters { get; }
+        string CommandText { get; set; }
+
+        int ExecuteNonQuery();
+    }
+}

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/ISqlConnectionFactory.cs

@@ -1,9 +1,7 @@
-using System.Data.SqlClient;
-
-namespace Serilog.Sinks.MSSqlServer.Sinks.MSSqlServer.Platform
+namespace Serilog.Sinks.MSSqlServer.Sinks.MSSqlServer.Platform
 {
     internal interface ISqlConnectionFactory
     {
-        SqlConnection Create();
+        ISqlConnectionWrapper Create();
     }
 }

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/ISqlConnectionWrapper.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Data.SqlClient;
+using System.Threading.Tasks;
+
+namespace Serilog.Sinks.MSSqlServer.Sinks.MSSqlServer.Platform
+{
+    internal interface ISqlConnectionWrapper : IDisposable
+    {
+        SqlConnection SqlConnection { get; }
+
+        void Open();
+        Task OpenAsync();
+        ISqlCommandWrapper CreateCommand();
+    }
+}

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/SqlBulkBatchWriter.cs

@@ -44,8 +44,8 @@ public async Task WriteBatch(IEnumerable<LogEvent> events, DataTable dataTable)
                 {
                     await cn.OpenAsync().ConfigureAwait(false);
                     using (var copy = _disableTriggers
-                            ? new SqlBulkCopy(cn)
-                            : new SqlBulkCopy(cn, SqlBulkCopyOptions.CheckConstraints | SqlBulkCopyOptions.FireTriggers, null)
+                            ? new SqlBulkCopy(cn.SqlConnection)
+                            : new SqlBulkCopy(cn.SqlConnection, SqlBulkCopyOptions.CheckConstraints | SqlBulkCopyOptions.FireTriggers, null)
                     )
                     {
                         copy.DestinationTableName = string.Format(CultureInfo.InvariantCulture, "[{0}].[{1}]", _schemaName, _tableName);

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/SqlCommandWrapper.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Data;
+using System.Data.Common;
+using System.Data.SqlClient;
+
+namespace Serilog.Sinks.MSSqlServer.Sinks.MSSqlServer.Platform
+{
+    internal class SqlCommandWrapper : ISqlCommandWrapper
+    {
+        private readonly SqlCommand _sqlCommand;
+        private bool _disposedValue;
+
+        public SqlCommandWrapper(SqlCommand sqlCommand)
+        {
+            _sqlCommand = sqlCommand ?? throw new ArgumentNullException(nameof(sqlCommand));
+        }
+
+        public CommandType CommandType
+        {
+            get => _sqlCommand.CommandType;
+            set => _sqlCommand.CommandType = value;
+        }
+
+        public DbParameterCollection Parameters => _sqlCommand.Parameters;
+
+        public string CommandText
+        {
+            get => _sqlCommand.CommandText;
+            set => _sqlCommand.CommandText = value;
+        }
+
+        public int ExecuteNonQuery() =>
+            _sqlCommand.ExecuteNonQuery();
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposedValue)
+            {
+                _sqlCommand.Dispose();
+                _disposedValue = true;
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(disposing: true);
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/SqlConnectionFactory.cs

@@ -20,13 +20,13 @@ public SqlConnectionFactory(string connectionString, IAzureManagedServiceAuthent
                 ?? throw new ArgumentNullException(nameof(azureManagedServiceAuthenticator));
         }
 
-        public SqlConnection Create()
+        public ISqlConnectionWrapper Create()
         {
             var sqlConnection = new SqlConnection(_connectionString);
-
             _azureManagedServiceAuthenticator.SetAuthenticationToken(sqlConnection);
 
-            return sqlConnection;
+            var sqlConnectionWrapper = new SqlConnectionWrapper(sqlConnection);
+            return sqlConnectionWrapper;
         }
     }
 }

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/SqlConnectionWrapper.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Data.SqlClient;
+using System.Threading.Tasks;
+
+namespace Serilog.Sinks.MSSqlServer.Sinks.MSSqlServer.Platform
+{
+    internal class SqlConnectionWrapper : ISqlConnectionWrapper
+    {
+        private readonly SqlConnection _sqlConnection;
+        private bool _disposedValue;
+
+        public SqlConnectionWrapper(SqlConnection sqlConnection)
+        {
+            _sqlConnection = sqlConnection ?? throw new ArgumentNullException(nameof(sqlConnection));
+        }
+
+        public SqlConnection SqlConnection => _sqlConnection;
+
+        public void Open()
+        {
+            _sqlConnection.Open();
+        }
+
+        public async Task OpenAsync()
+        {
+            await _sqlConnection.OpenAsync().ConfigureAwait(false);
+        }
+
+        public ISqlCommandWrapper CreateCommand()
+        {
+            var sqlCommand = _sqlConnection.CreateCommand();
+            return new SqlCommandWrapper(sqlCommand);
+        }
+
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposedValue)
+            {
+                _sqlConnection.Dispose();
+                _disposedValue = true;
+            }
+        }
+
+        public void Dispose()
+        {
+            Dispose(disposing: true);
+            GC.SuppressFinalize(this);
+        }
+    }
+}

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/SqlLogEventWriter.cs

@@ -34,7 +34,7 @@ public void WriteEvent(LogEvent logEvent)
                 using (var connection = _sqlConnectionFactory.Create())
                 {
                     connection.Open();
-                    using (SqlCommand command = connection.CreateCommand())
+                    using (ISqlCommandWrapper command = connection.CreateCommand())
                     {
                         command.CommandType = CommandType.Text;
 

src/Serilog.Sinks.MSSqlServer/Sinks/MSSqlServer/Platform/SqlTableCreator.cs

@@ -35,7 +35,7 @@ public void CreateTable(DataTable dataTable)
                 using (var conn = _sqlConnectionFactory.Create())
                 {
                     var sql = _sqlCreateTableWriter.GetSqlFromDataTable(_schemaName, _tableName, dataTable, _columnOptions);
-                    using (var cmd = new SqlCommand(sql, conn))
+                    using (var cmd = new SqlCommand(sql, conn.SqlConnection))
                     {
                         conn.Open();
                         cmd.ExecuteNonQuery();

test/Serilog.Sinks.MSSqlServer.Tests/Sinks/MSSqlServer/Platform/SqlBulkBatchWriterTests.cs

@@ -0,0 +1,6 @@
+namespace Serilog.Sinks.MSSqlServer.Tests.Sinks.MSSqlServer.Platform
+{
+    public class SqlBulkBatchWriterTests
+    {
+    }
+}