class Student(object):    def __init__(self, name, score):        self.name = name        self.score = score    def get_grade(self):        if self.score > 100:            raise ValueError        elif self.score >= 80:            return "A"        elif self.score >= 60:            return "B"        elif self.score < 0:            raise ValueError        else:            return "C"import unittestclass TestStudent(unittest.TestCase):    def test_80_to_100(self):        s1 = Student("Bar", 80)        s2 = Student("Aar", 100)        self.assertEquals(s1.get_grade(), "A")        self.assertEquals(s2.get_grade(), "A")    def test_60_to_80(self):        s1 = Student("Car", 60)        s2 = Student("Dar", 79)        self.assertEquals(s1.get_grade(), "B")        self.assertEquals(s2.get_grade(), "B")    def test_0_60(self):        s1 = Student("Ear", 0)        s2 = Student("Far", 59)        self.assertEquals(s1.get_grade(), "C")        self.assertEquals(s2.get_grade(), "C")    def test_invalid(self):        s1 = Student("Gar", -1)        s2 = Student("Har", 101)        with self.assertRaises(ValueError):            s1.get_grade()        with self.assertRaises(ValueError):            s2.get_grade()if __name__ == '__main__':    unittest.main

很好，学到了