require File.expand_path(File.dirname(__FILE__)+"/spec_helper.rb")
  
describe Distribution::Exponential do
    
  shared_examples_for "exponential engine" do
    it "should return correct pdf" do
      if @engine.respond_to? :pdf
        [0.5,1,1.5].each {|l|
          1.upto(5) {|x|
            @engine.pdf(x,l).should be_within(1e-10).of(l*Math.exp(-l*x))
          }
        }
      else
        pending("No #{@engine}.pdf")
      end
    end
    
    it "should return correct cdf" do
      if @engine.respond_to? :cdf
        [0.5,1,1.5].each {|l|
          1.upto(5) {|x|
            @engine.cdf(x,l).should be_within(1e-10).of(1-Math.exp(-l*x))
          }
        }
      else
        pending("No #{@engine}.cdf")
      end
    end
  
    
    it "should return correct p_value" do
      if @engine.respond_to? :p_value
        [0.5,1,1.5].each {|l|
          1.upto(5) {|x|
            pr=@engine.cdf(x,l)
            @engine.p_value(pr,l).should be_within(1e-10).of(x)
          }
        }
      else
        pending("No #{@engine}.p_value")
      end
    end
  end
  

  describe "singleton" do
    before do
      @engine=Distribution::Exponential
    end
    it_should_behave_like "exponential engine"
  end
  
  describe Distribution::Exponential::Ruby_ do
    before do
      @engine=Distribution::Exponential::Ruby_
    end
    it_should_behave_like "exponential engine"
    
  end
    
  if Distribution.has_gsl?
    describe Distribution::Exponential::GSL_ do
      before do
        @engine=Distribution::Exponential::GSL_
      end
    it_should_behave_like "exponential engine"
    end
  end
  
#  if Distribution.has_java?
#    describe Distribution::Exponential::Java_ do
#      before do
#        @engine=Distribution::Exponential::Java_
#      end
#    it_should_behave_like "exponential engine"
#    
#    end  
#  end
  describe "rng" do
    it "should default to Kernel#rand if no :random is given" do
      Random.stub(:rand)
      Random.should_receive(:rand).and_return(0.5)
      rng = Distribution::Exponential.rng 1.0
      rng.call()
    end

    it "should use a given rng if one is passed during construction" do
      random = double("random")
      random.should_receive(:rand).and_return(0.5)
      rng = Distribution::Exponential::rng 1.0, :random => random
      rng.call()
    end
  end  
end