def test_sell():
p = Portfolio()
p.buy("MSFT", 100, 27.0)
p.buy("DELL", 100, 17.0)
p.buy("ORCL", 100, 34.0)
p.sell("MSFT", 50)
assert p.cost() == 6450
def test_empty():
p = Portfolio()
assert p.cost() == 0.0
def test_buy_two_stocks():
p = Portfolio()
p.buy("IBM", 100, 176.48)
p.buy("HPQ", 100, 36.15)
assert p.cost() == 21263.0
def test_buy_one_stock():
p = Portfolio()
p.buy("IBM", 100, 176.48)
assert p.cost() == 17648.0
