def test_add():
'It tests the add method'
seq = Seq('AC') + Seq('TG')
assert seq == 'ACTG'
assert seq.complement() #is still a Seq
def test_complement():
'It test the Seq complement method'
seq = Seq('ACTG')
seq2 = seq.complement()
assert seq2 == 'TGAC'
