# WARNING: pseudo code

class Authenticator
  def initialize(user_repository = User)
    @user_repository = user_repository
  end

  def authenticate(identifier, hashed_password)
    @user_repository.find(:username => identifier, :password => hashed_password).present?
  end
end

describe Authenticator
  let(:repo) { double("user repo") }
  let(:authenticator) { Authenticator.new(repo) }

  context "with invalid credentials"
    before { repo.stub(:find => nil) }

    it "returns false" do
      authenticator.authenticate("invalid", "invalid").should_not be
    end
  end

  context "with valid credentials"
    before { repo.stub(:find => double) }

    it "returns true" do
      authenticator.authenticate("valid", "valid").should be
    end
  end
end