How to support addition IDbConnection methods in Dapper (using DapperWrapper)?

How to support addition IDbConnection methods in Dapper (using
DapperWrapper)?

I'm attempting to create some unit tests for a repository that uses Dapper
methods, but I'm having trouble figuring out how to get my code to accept
a mocked DbConnection. I found that DapperWrapper acknowledges this
problem and accomplishes most of what I need, but the IDbExecutor
interface it provides does not include some of the base IDbConnection's
methods I need in my code to open and close the connection.
For example, below is a property from my base repository class that
defines the database connection used in all the repositories, retrieves it
from a factory, and Opens the connection if it's closed or doesn't yet
exist. This code doesn't work because IDbExecutor does not expose the Open
or Close methods, nor can there be a State property on the interface.
private IDbExecutor _db;
protected IDbExecutor Db
{
get
{
if (_db == null)
{
_db = DbConnectionFactory.GetConnection();
_db.Open();
}
else if (_db != null && _db.State != ConnectionState.Open)
{
_db.Open();
}
return _db;
}
set
{
_db = value;
}
}
Is there a way to extend or inherit the IDbExecutor in such a way that I
can reference these methods and properties for the SQL connection (and in
my mock connection object)? Or is there a better approach to this whole
problem?