old_contents: import rml.lattice
  
  def test_create_lattice():
      l = rml.lattice.Lattice()
      assert(len(l)) == 0
  
  def test_non_negative_lattice():
      l = rml.lattice.Lattice()
      assert(len(l)) >= 0
  
new_contents: import rml.lattice
  import rml.element
  
  def test_create_lattice():
      l = rml.lattice.Lattice()
      assert(len(l)) == 0
  
  
  def test_non_negative_lattice():
      l = rml.lattice.Lattice()
      assert(len(l)) >= 0
  
  
  def test_lattice_with_one_element():
      l = rml.lattice.Lattice()
      element_length = 1.5
      e = rml.element.Element('dummy', element_length)
      l.append_element(e)
      # There is one element in the lattice.
      assert(len(l) == 1)
      # The total length of the lattice is the same as its one element.
      assert l.length() = element_length
  
  
subject: Test simple lattice with one element.