Mocking Membership

I'm writing a custom Profile provider, but I still intend to use the default AspNetSqlMembershipProvider as my Membership provider.  My GetAllProfiles() method in my Profile provider looks like this:
1    public override ProfileInfoCollection GetAllProfiles(ProfileAuthenticationOption authenticationOption, int pageIndex, int pageSize, out int totalRecords)
2    {
3        // Get the profiles
4        IQueryable<Profile> profiles = _profileRepository.GetAllProfiles();
5   
6        // Convert to a ProfileInfoCollection
7      &nbs ...