def testAddition(self):
        "Test addition & subtraction"
        a1 = A(sq_m=100)
        a2 = A(sq_m=200)

        a3 = a1 + a2
        self.assertEqual(a3.sq_m, 300)
        a3 += a1
        self.assertEqual(a3.sq_m, 400)
        
        a4 = a1 - a2
        self.assertEqual(a4.sq_m, -100)
        a4 -= a1
        self.assertEqual(a4.sq_m, -200)
        
        try:
            a5 = a1 + 1
        except TypeError, e:
            pass
        else:
            self.fail('Area + number should raise TypeError')

        try:
            a5 = 1 - a1
        except TypeError, e:
            pass
        else:
            self.fail('Area - number should raise TypeError')

        try:
            a1 += 1
        except TypeError, e:
            pass
        else:
            self.fail('Area += number should raise TypeError')

        try:
            a1 -= 1
        except TypeError, e:
            pass
        else:
            self.fail('Area -= number should raise TypeError')
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/django/contrib/gis/tests/test_measure.py/AreaTest.testAddition/swapped operands of `-`