def test_0(self):
     self.assertEqual(korean_number(0), '영')
 def test_1(self):
     self.assertEqual(korean_number(1), '일')
 def test_41(self):
     self.assertEqual(korean_number(41), '사십일')
 def test_100(self):
     self.assertEqual(korean_number(100), '백')
 def test_31(self):
     self.assertEqual(korean_number(31), '삼십일')
 def test_21(self):
     self.assertEqual(korean_number(21), '이십일')
 def test_20(self):
     self.assertEqual(korean_number(20), '이십')
 def test_12(self):
     self.assertEqual(korean_number(12), '십이')
 def test_2(self):
     self.assertEqual(korean_number(2), '이')