'Get the min course price for a course according to currency'

def test_min_course_price_for_currency(self):

    self.assertEqual(0, CourseMode.min_course_price_for_currency(self.course_key, 'usd'))
    mode1 = Mode(u'honor', u'Honor    Code    Certificate', 10, '', 'usd', None, None, None, None)
    mode2 = Mode(u'verified', u'Verified    Certificate', 20, '', 'usd', None, None, None, None)
    mode3 = Mode(u'honor', u'Honor    Code    Certificate', 80, '', 'cny', None, None, None, None)
    set_modes = [mode1, mode2, mode3]
    for mode in set_modes:
        self.create_mode(mode.slug, mode.name, mode.min_price, mode.suggested_prices, mode.currency)
    self.assertEqual(10, CourseMode.min_course_price_for_currency(self.course_key, 'usd'))
    self.assertEqual(80, CourseMode.min_course_price_for_currency(self.course_key, 'cny'))
