require 'test/unit'
require 'test/framework'

require 'units'

class TC_unit_derive < Test::Unit::TestCase

  understands UnitsTest

  def test_unit_derived

    length =
      Units.create :length do |m|
        m.system :metric do |s|
          s.unit :name => :meter,
                 :abbrev => :m,
                 :greek => :ten
        end
        m.system :english do |s|
          s.unit :name => :inch,
                 :plural => :inches,
                 :abbrev => :in
          s.unit :name => :foot,
                 :plural => :feet,
                 :abbrev => :ft,
                 :equals => 12.inches
          s.unit :name => :yard,
                 :abbrev => :yd,
                 :equals => 3.feet
        end
      end
    
    centimeter = length.metric.centimeter
    inch = length.english.inch
    foot = length.english.foot
    yard = length.english.yard

    volume =
      Units.derive :volume, length**3 do |m|
        m.system :metric do |s|
          s.unit :name => :milliliter,
                 :abbrev => :mL,
                 :equals => 1.cm**3
        end
      end
    
    assert(volume.derived.size == 1)
    assert(volume.derived[length] == 3)
    milliliter = volume.metric.milliliter

    mass = 
      Units.create :mass do |m|
        m.system :metric do |s|
          s.unit :name => :gram,
                 :abbrev => :g,
                 :greek => :ten
        end
      end

    gram = mass.metric.gram

    density =
      Units.derive :density, mass/volume do |m|
        m.system :base do |s|
          s.unit :name => :foo,
                 :equals => 1.g/1.mL
        end
      end
    
    assert(density.derived.size == 2)
    assert(density.derived[length] == -3)
    assert(density.derived[mass] == 1)
    
    area =
      Units.derive :area, length**2 do |m|
        m.system :english do |s|
          s.unit :name => :acre,
                 :equals => 220.yards * 66.feet
        end
      end
    
    assert(area.derived.size == 1)
    assert(area.derived[length] == 2)
    
  end
    
end