require 'test/unit'
require 'factorial'
class TestFactorial < Test::Unit::TestCase
   def test_calc
      f = Factorial.new
      assert_equal(120, f.calc(5) )
      assert_equal(1, f.calc(1) )
      assert_equal(1, f.calc(0) )
      assert_nil(f.calc(1.3) )
      assert_nil(f.calc(-1) )
      assert_nil(f.calc("text"))
   end
end