import unittest class Student(object): def init(self, name, score): self.name = name self.score = score def get_grade(self): if self.score >= 60 and self.score < 80: return 'B' if self.score >= 80 and self.score <= 100: return 'A' if self.score < 60 and self.score >=0: return 'C' else: raise ValueError("scores'value is wrong") class TestStudent(unittest.TestCase):

def test_80_to_100(self):
    s1 = Student('Bart', 80)
    s2 = Student('Lisa', 100)
    self.assertEqual(s1.get_grade(), 'A')
    self.assertEqual(s2.get_grade(), 'A')

def test_60_to_80(self):
    s1 = Student('Bart', 60)
    s2 = Student('Lisa', 79)
    self.assertEqual(s1.get_grade(), 'B')
    self.assertEqual(s2.get_grade(), 'B')

def test_0_to_60(self):
    s1 = Student('Bart', 0)
    s2 = Student('Lisa', 59)
    self.assertEqual(s1.get_grade(), 'C')
    self.assertEqual(s2.get_grade(), 'C')

def test_invalid(self):
    s1 = Student('Bart', -1)
    s2 = Student('Lisa', 101)
    with self.assertRaises(ValueError):
        s1.get_grade()
    with self.assertRaises(ValueError):
        s2.get_grade()

if name == 'main': unittest.main()