Add DuckDB tests

Directory.Packages.props

@@ -1,6 +1,7 @@
 <Project>
     <ItemGroup>
       <!-- note: 6.2.0 has regressions; don't force the update -->
+      <PackageVersion Include="DuckDB.NET.Data.Full" Version="0.9.0.3" />
       <PackageVersion Include="EntityFramework" Version="6.1.3" />
       <PackageVersion Include="Microsoft.CSharp" Version="4.7.0" />
       <PackageVersion Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" />

tests/Dapper.Tests/Dapper.Tests.csproj

@@ -15,6 +15,7 @@
   <ItemGroup>
     <ProjectReference Include="../../Dapper.ProviderTools/Dapper.ProviderTools.csproj" />
     <ProjectReference Include="../../Dapper.SqlBuilder/Dapper.SqlBuilder.csproj" />
+    <PackageReference Include="DuckDB.NET.Data.Full" />
     <PackageReference Include="FirebirdSql.Data.FirebirdClient" />
     <PackageReference Include="Microsoft.Data.SqlClient" />
     <PackageReference Include="Microsoft.Data.Sqlite" />

tests/Dapper.Tests/Providers/DuckDBTests.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Data.Common;
+using DuckDB.NET.Data;
+using Xunit;
+
+namespace Dapper.Tests
+{
+    public class DuckDBProvider : DatabaseProvider
+    {
+        public override DbProviderFactory Factory => DuckDBClientFactory.Instance;
+        public override string GetConnectionString() => "Data Source=:memory:";
+    }
+
+    public abstract class DuckDBTypeTestBase : TestBase<DuckDBProvider>
+    {
+        protected DuckDBConnection GetDuckDBConnection(bool open = true)
+            => (DuckDBConnection)(open ? Provider.GetOpenConnection() : Provider.GetClosedConnection());
+
+        [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
+        public class FactDuckDBAttribute : FactAttribute
+        {
+            public override string? Skip
+            {
+                get { return unavailable ?? base.Skip; }
+                set { base.Skip = value; }
+            }
+
+            private static readonly string? unavailable;
+
+            static FactDuckDBAttribute()
+            {
+                try
+                {
+                    using var _ = DatabaseProvider<DuckDBProvider>.Instance.GetOpenConnection();
+                }
+                catch (Exception ex)
+                {
+                    unavailable = $"DuckDB is unavailable: {ex.Message}";
+                }
+            }
+        }
+    }
+
+    public class DuckDBTests : DuckDBTypeTestBase
+    {
+        [FactDuckDB]
+        public void DuckDBNamedParameter()
+        {
+            using var connection = GetDuckDBConnection();
+
+            var result = connection.QueryFirst<int>("Select $foo", new {foo = 42});
+            Assert.Equal(42, result);
+        }
+
+        [FactDuckDB]
+        public void DuckDBPositionalParameter()
+        {
+            using var connection = GetDuckDBConnection();
+
+            var dp = new DynamicParameters();
+            dp.Add("?", 42);
+
+            var result = connection.QueryFirst<int>("Select ?", dp);
+            Assert.Equal(42, result);
+        }
+    }
+}