Rspec testing in ruby mine always returns false

I have a class User as follows

class User < ActiveRecord::Base

  has_one :session
  has_and_belongs_to_many :posts
  has_and_belongs_to_many :replies

  attr_accessor :clear_text_password;

  validates_presence_of :username
  validates_uniqueness_of :username
  validates :clear_text_password, :presence => true, :length => {:minimum => 6}
  validates_confirmation_of :clear_text_password

  validates_presence_of :e_mail
  validates_uniqueness_of :e_mail

  def User.authenticate(name, password)
    if user = find_by_username(name)
      if user.password == encrypt_password(password)
        user

      end
    end
  end

end 

Now, my rspec test file is as below

require 'spec_helper'
require 'rspec'
require 'rspec-rails'
require 'user'

describe User do
  describe "my first test" do
    it "should redirect if user is authenticated" do
      user = User.authenticate('abcd','abcdef')
      c=false
      if user
        c=true
      end
      c.should == true

    end
  end
end

The databas开发者_开发知识库e table users has the username and password "abcd" and "abcdef" . but the test always fails. the method call always returns false. Please help!!