C# Online Compiler | .NET Fiddle

using System;
using Dapper;
using Moq;
using Moq.Dapper;
using System.Data;
using System.Data.Common;
using System.Linq;
using System.Collections.Generic;
					
public class Program
{
	public class ComplexType
	{
		public string StringProperty { get; set; }
		public int IntegerProperty { get; set; }
	}

	private static void TestMoqDapperExecuteAsyncDbConnection()
	{
            var connection = new Mock<DbConnection>();

            connection.SetupDapperAsync(c => c.ExecuteAsync("", null, null, null, null))
                      .ReturnsAsync(1);

            var result = connection.Object
                                   .ExecuteAsync("")
                                   .GetAwaiter()
                                   .GetResult();
		
		Console.WriteLine(string.Format("ExecuteAsync<DbConnection> Test {0}", result == 1 ? "PASSED" : "FAILED"));
	}
	
	private static void TestMoqDapperExecuteAsyncIDbConnection()
	{
            var connection = new Mock<IDbConnection>();
		    var tran= new Mock<IDbTransaction>();

            connection.SetupDapperAsync(c => c.QueryAsync<int>(It.IsAny<string>(), It.IsAny<object>(), It.IsAny<IDbTransaction>(), It.IsAny<int>(), It.IsAny<CommandType>()))
                      .ReturnsAsync(new List<int>
            {
                5
            });
		

            var result = connection.Object
                                   .QueryAsync<int>("",null,tran.Object)
                                   .GetAwaiter()
                                   .GetResult();

		Console.WriteLine("3");
		Console.WriteLine(result.Count());
		Console.WriteLine(string.Format("ExecuteAsync<DbConnection> Test {0}", result.Count() != 0 ? "PASSED" : "FAILED"));
	}
	
	public static void Main()
	{
		// This test will pass.
		TestMoqDapperExecuteAsyncDbConnection();
		
		// This test will throw an exception because Moq.Dapper doesn't support IDbConnection.ExecuteAsync(), even though it supports DbConnection.ExecuteAsync()
		TestMoqDapperExecuteAsyncIDbConnection();
	}
}

 
using System;
using Dapper;
using Moq;
using Moq.Dapper;
using System.Data;
using System.Data.Common;
using System.Linq;
using System.Collections.Generic;
                    
public class Program
{
    public class ComplexType
    {
        public string StringProperty { get; set; }
        public int IntegerProperty { get; set; }
    }
​
    private static void TestMoqDapperExecuteAsyncDbConnection()
    {
            var connection = new Mock<DbConnection>();
​
            connection.SetupDapperAsync(c => c.ExecuteAsync("", null, null, null, null))
                      .ReturnsAsync(1);
​