def test_default_value
   hash1 = Hash.new
   hash1[:one] = 1

   assert_equal 1, hash1[:one]
   assert_equal nil, hash1[:two]

   hash2 = Hash.new("dos")
   hash2[:one] = 1

   assert_equal 1, hash2[:one]
   assert_equal nil, hash2[:two]
 end