require File.expand_path(File.dirname(__FILE__)+"/spec_helper.rb")
  
describe Distribution::Logistic do
    
  shared_examples_for "logistic engine" do
    it "should return correct pdf" do
      if @engine.respond_to? :pdf
        1.upto(10) {
	u=rand()
        s=rand()+1
        x=rand()*100-50
        exp=Math.exp(-(x-u) / s) / (s*(1+Math.exp(-(x-u) / s)**2))
        @engine.pdf(x,u,s).should eq(exp)
        }
      else
        pending("No #{@engine}.pdf")
       end
    end
    
    it "should return correct cdf" do
      if @engine.respond_to? :cdf


        1.upto(100) {
	u=rand()
        s=rand()+1
        x=rand()*100-50
	exp=1/(1+Math.exp(-(x-u)/s))
	@engine.cdf(x,u,s).should eq(exp)
        }
      
      else
        pending("No #{@engine}.cdf")
      end
    end
  
    
    it "should return correct p_value" do
      if @engine.respond_to? :p_value
       1.upto(9) {|i|
       u=rand()
       s=rand()+1
       x=@engine.p_value(i/10,u,s)
       @engine.cdf(x,u,s).should eq i/10
        }
      else
        pending("No #{@engine}.cdf")
      end
    end
  end
  

  describe "singleton" do
    before do
      @engine=Distribution::Logistic
    end
    it_should_behave_like "logistic engine"
  end
  
  describe Distribution::Logistic::Ruby_ do
    before do
      @engine=Distribution::Logistic::Ruby_
    end
    it_should_behave_like "logistic engine"
    
  end
    
end