public void GetAllUsersReturnsAllCreatedUsers()
{
const string username1 = "TestUser1";
const string username2 = "TestUser2";
var repository = new InMemoryUserRepository();
var createdUser1 = repository.CreateUser(username1);
var createdUser2 = repository.CreateUser(username2);
var allUsers = repository.GetAllUsers().ToList();
Assert.That(allUsers.Count, Is.EqualTo(2));
Assert.That(allUsers, Contains.Item(createdUser1));
Assert.That(allUsers, Contains.Item(createdUser2));
}