how to handle Collections

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;


namespace MockCollectionTestConsole
{
   class Program
   {
      static void Main(string[] args)
      {
         User u = new User();

         if (IsAddressValid(u, "hardcoded2"))
            Console.WriteLine("match");

      }

      static bool IsAddressValid(User user, string validStreet)
      {
         bool result = false;

         foreach (Address a in user.Addresses)
         {
            if (a.Street == validStreet)
            {
               result = true;
               break;
            }
         }

         return result;
      }
   }

   public class User
   {
      private AddressCollection _addresses = new AddressCollection();

      public AddressCollection Addresses { get { return this._addresses; } }
   }

   public class Address
   {
      private string _street = string.Empty;

      public string Street
      {
         get { return _street; }
         set { _street = value; }
      }

      public Address(string street)
      {
         this._street = street;
      }
   }

   public class AddressCollection : IEnumerable<Address>
   {
      private List<Address> _list = new List<Address>();

      public AddressCollection()
      {
         this._list.Add(new Address("hardcoded1"));
         this._list.Add(new Address("hardcoded2"));
         this._list.Add(new Address("hardcoded3"));
      }

      #region IEnumerable Members

      public IEnumerator<Address> GetEnumerator()
      {
         return this._list.GetEnumerator();
      }

      System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
      {
         return ((IEnumerable)this._list).GetEnumerator();
      }

      #endregion
   }
   
}

[DeploymentItem("MockCollectionTestConsole.exe")]
[TestMethod()]
public void IsMatchStreetTest()
{
   using (RecordExpectations recorder = RecorderManager.StartRecording())
   {
// WHAT TO PUT HERE SUCH THAT I CAN SET THE COLLECTION OF user.Addresses in the IsAddressValid method to whatever I want????
//
// FOR EXAMPLE, LET"S SAY I WANT user.Addresses TO CONTAIN 2 Address OBJECTS, THAT
// RETURN "test1" AND "test2" FOR THE Street PROPERTY
//
// WHAT IS THE BEST WAY TO DO THAT?
   }

      User user = new User();

      string toMatch = "test2";

      bool expected = true;
      bool actual;

      actual = MockTestProject.MockCollectionTestConsole_ProgramAccessor.IsAddressValid(user, toMatch);

      Assert.AreEqual(expected, actual, "MockCollectionTestConsole.Program.IsMatchStreet did not return the expected value");
   }
}