def test_lsb(self):
"""
Test LSB
"""
n1 = Diagram()
n1.id = 'n1'
n2 = PackagingElement('a', id='n2')
n3 = PackagingElement('a', id='n3')
n4 = PackagingElement('a', id='n4')
n1.children.extend((n2, n3))
n2.children.append(n4)
n2.parent = n1
n3.parent = n1
n4.parent = n2
siblings = lsb(n1, n3, n4)
self.assertEquals([n3, n2], siblings)