How I can stub IDBconnection

I am writting Unit Test for my database connection.

I have following class

    Public class A
        {
            public IDbConnection _dbConnection;

     public A()
     {
        _dbConnection = new SqlConnection(connectionStringName);
      }

            public int ExecuteNoneQuery(CommandDefination command)
            {
               return _dbConnection.Execute(command);
            }
        }

I want to test this class, how I can test with Microsoft Stub/Shim

I have written following code, but it is not working.

 [TestMethod]
        public void TestMethod1()
        {
            StubIDbConnection stubIDbConnection = new StubIDbConnection();
            stubIDbConnection.Execute =(null) => -1;
            var a = new classA();
            int answer = a.ExecuteNoneQuery(null);
            Assert.AreEqual(-1,-1);

         }