Winter '12 Force.com Platform Release
Public Test Classes in Apex

Classes annotated with @isTest no longer have to be private. You can now create public test classes that expose common methods for test data creation. These public methods can be called by tests outside the test class for setting up data that the tests need to run against.

This is an example of a public test class that contains utility methods for test data creation:

@IsTest
public class TestUtil {
  public static void createTestAccounts() {
    // Create some test accounts
  }
  public static void createTestContacts() {
    // Create some test contacts
  }
}