def test_get_span_complement(self):
diag = Diagram([(1, 4), (2, 5), (3, 8), (6, 7)])
span = Span(4, 5)
cspan = diag.get_span_complement(span)
self.assertEqual(cspan, Span(1, 2))
ccspan = diag.get_span_complement(cspan)
self.assertEqual(span, ccspan) # Double complement returns original
def test_get_span_complement_of_chord(self):
diag = Diagram([(1, 4), (2, 5), (3, 8), (6, 7)])
span = Span(1, 4)
cspan = diag.get_span_complement(span)
self.assertEqual(span, cspan) # Complement of a chord is itself