'Test that when we try context.portfolio.positions[stock] on a stock
for which we have no positions, we return a Position with values 0
(but more importantly, we don\'t crash) and don\'t save this Position
to the user-facing dictionary PositionTracker._positions_store'

def test_empty_positions(self):

    algo = TradingAlgorithm(script=empty_positions, sim_params=self.sim_params, env=self.env)
    results = algo.run(self.data_portal)
    num_positions = results.num_positions
    amounts = results.amounts
    self.assertTrue(all((num_positions == 0)))
    self.assertTrue(all((amounts == 0)))
