def test_pr2bias(self):
"""CodonUsage pr2bias should give correct ratios."""
c = EqualBases.codons()
b = c.pr2bias('UU')
self.assertEqual(len(b), 6)
self.assertEqual(b, tuple([.5]*6))
c = CodonUsage()
c['ACU'] = 10
c['ACC'] = 5
c['ACA'] = 15
c['ACG'] = 20
self.assertEqual(c.pr2bias('AC'), (20/25,15/25,20/35,5/15,20/30,5/20))
