C# Online Compiler | .NET Fiddle

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

	private static void TestMoqDapperExecuteAsyncDbConnection()
	{
		
		Console.WriteLine("Running ExecuteAsync<DbConnection> Test...");
		
		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}\r\n", result == 1 ? "PASSED" : "FAILED"));
	}
	
	private static void TestMoqDapperExecuteAsyncIDbConnection()
	{
		int result = 0;
		
		Console.WriteLine("Running ExecuteAsync<IDbConnection> Test...");
		
		try
		{
            var connection = new Mock<IDbConnection>();

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

            result = connection.Object
                                   .ExecuteAsync("")
                                   .GetAwaiter()
                                   .GetResult();
		}
		catch (Exception ex)
		{
			Console.WriteLine(ex);
		}
		
		Console.WriteLine(string.Format("ExecuteAsync<IDbConnection> Test {0}\r\n", result == 1 ? "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();
	}
}

        // This test will throw an exception because Moq.Dapper doesn't support IDbConnection.ExecuteAsync(), even though it supports DbConnection.ExecuteAsync()
 
using System;
using Dapper;
using Moq;
using Moq.Dapper;
using System.Data;
using System.Data.Common;
using System.Linq;
                    
public class Program
{
    public class ComplexType
    {
        public string StringProperty { get; set; }
        public int IntegerProperty { get; set; }
    }
​
    private static void TestMoqDapperExecuteAsyncDbConnection()
    {
        
        Console.WriteLine("Running ExecuteAsync<DbConnection> Test...");
        
        var connection = new Mock<DbConnection>();
​
        connection.SetupDapperAsync(c => c.ExecuteAsync("", null, null, null, null))

Cached Result

Root Default namespace:
Ok
Header Default namespace: