'Test the parallel resistor operator ||
The formula is given by
a || b || c ...
= 1 / (1/a + 1/b + 1/c + ...)
It is the resistance of a parallel circuit of resistors with resistance
a, b, c, etc&. See if this evaulates correctly.'

def test_parallel_resistors(self):

    self.assertEqual(calc.evaluator({}, {}, '1||1'), 0.5)
    self.assertEqual(calc.evaluator({}, {}, '1||1||2'), 0.4)
    self.assertEqual(calc.evaluator({}, {}, 'j||1'), (0.5 + 0.5j))
