def test_weight_with_empty_string(self):
		self.assertFalse(Donor.is_valid_weight(''))
	def test_weight_with_zero(self):
		self.assertFalse(Donor.is_valid_weight('0'))
	def test_weight_with_letters(self):
		self.assertFalse(Donor.is_valid_weight('abc'))
	def test_weight_with_valid_string(self):
		self.assertTrue(Donor.is_valid_weight('50'))