def test_true_2(self):
     self.assertTrue(balls_collide((0.0, 0.0, 0.0), (5.0, 5.7, 20.0)))
 def test_true_1(self):
     self.assertTrue(balls_collide((5.5, 2.4, 8.0), (5.0, 5.7, 2.0)))
 def test_false_2(self):
     self.assertFalse(balls_collide((1.5, 1.5, 2.0), (7.0, 5.7, 2.0)))
 def test_false_1(self):
     self.assertFalse(balls_collide((-8.5, -7.4, 2.0), (5.0, 5.7, 1.0)))
 def test_true_4(self):
     self.assertTrue(balls_collide((2.0, 0.0, 1.0), (0.0, 0.0, 1.0)))
 def test_true_3(self):
     self.assertTrue(balls_collide((1.0, 1.0, 1.0), (1.0, 1.0, 1.0)))