How to use the qstrader.broker.portfolio.position.Position function in qstrader

def test_position_representation():
    """
    Tests that the Position representation
    correctly recreates the object.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset, quantity=153,
        book_cost_pu=950.0,
        current_price=950.0
    )
    exp_repr = (
        "Position(asset=Equity(name='Apple, Inc.', symbol='AAPL', tax_exempt=True), "
        "quantity=153, book_cost_pu=950.0, current_price=950.0)"
    )
    assert repr(position) == exp_repr

def test_position_long_short_negative_gain():
    """
    Tests that the quantity and book cost are
    correctly calculated for an initial long
    position with an additional short transaction
    in the same asset, where the short does not
    completely eliminate the position and the
    result is a loss.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset,
        quantity=100,
        book_cost_pu=960.0,
        current_price=950.0
    )

    dt = pd.Timestamp('2015-05-06')
    transaction = Transaction(
        asset,
        quantity=-50,
        dt=dt,
        price=950.0,
        order_id=123,
        commission=None
    )
    position.update(transaction)

def test_position_short_goes_to_half():
    """
    Tests that the quantity and book cost are
    correctly calculated for an initial short
    position, where the share value goes to zero.
    This should be a percentage gain of 100%.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset, quantity=-100, book_cost_pu=50.0,
        current_price=50.0
    )
    dt = pd.Timestamp('2015-05-06')
    position.current_price = 25.0
    position.current_trade_date = dt

    assert position.quantity == -100
    assert position.book_cost_pu == 50.0
    assert position.direction == -1.0
    assert position.current_price == 25.0
    assert position.market_value == -2500.0
    assert position.unrealised_gain == 2500.0
    assert position.unrealised_percentage_gain == 50.0

def test_position_long_close():
    """
    Tests that the quantity and book cost are
    correctly calculated for an initial long
    position with an additional short transaction
    in the same asset, where the short closes
    the position.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset,
        quantity=100,
        book_cost_pu=950.0,
        current_price=950.0
    )

    dt = pd.Timestamp('2015-05-06')
    transaction = Transaction(
        asset, quantity=-100, dt=dt, price=960.0,
        order_id=123, commission=None
    )
    position.update(transaction)

    assert position.quantity == 0
    assert position.book_cost_pu == 0.0
    assert position.direction == 1.0

def test_update_for_incorrect_asset():
    """
    Tests that the 'update' method, when provided
    with a transaction with an asset that does not
    match the position's asset, raises an Exception.
    """
    asset1 = Equity('Apple, Inc.', 'AAPL')
    asset2 = Equity('Amazon, Inc.', 'AMZN')

    position = Position(
        asset1, quantity=100, book_cost_pu=950.0,
        current_price=950.0
    )
    dt = pd.Timestamp('2015-05-06')
    transaction = Transaction(
        asset2, quantity=50, dt=dt, price=960.0,
        order_id=123, commission=None
    )

    with pytest.raises(Exception):
        position.update(transaction)

def test_position_short_long_excess_cover():
    """
    Tests that the quantity and book cost are
    correctly calculated for an initial short
    position with an additional long transaction
    in the same asset, where the long position
    is in excess of the short position.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset, quantity=-100, book_cost_pu=700.0,
        current_price=700.0
    )
    dt = pd.Timestamp('2015-05-06')
    transaction = Transaction(
        asset, quantity=175, dt=dt, price=873.0,
        order_id=123, commission=None
    )
    position.update(transaction)

    assert position.quantity == 75
    assert position.book_cost_pu == 873.0
    assert position.direction == 1.0
    assert position.current_price == 873.0
    assert position.market_value == 65475.0
    assert position.unrealised_gain == 0.0

def test_update_book_cost_for_commission_for_no_commission():
    """
    Tests that 'update_book_cost_for_commission' returns None
    when zero or None commission is provided.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset, quantity=100, book_cost_pu=950.0,
        current_price=950.0
    )

    assert position.update_book_cost_for_commission(asset, 0.0) is None
    assert position.update_book_cost_for_commission(asset, None) is None

def test_position_short_goes_to_zero():
    """
    Tests that the quantity and book cost are
    correctly calculated for an initial short
    position, where the share value goes to zero.
    This should be a percentage gain of 100%.
    """
    asset = Equity('Apple, Inc.', 'AAPL')
    position = Position(
        asset, quantity=-100, book_cost_pu=50.0,
        current_price=50.0
    )
    dt = pd.Timestamp('2015-05-06')
    position.current_price = 0.0
    position.current_trade_date = dt

    assert position.quantity == -100
    assert position.book_cost_pu == 50.0
    assert position.direction == -1.0
    assert position.current_price == 0.0
    assert position.market_value == 0.0
    assert position.unrealised_gain == 5000.0
    assert position.unrealised_percentage_gain == 100.0

def _check_set_position(self, asset):
        """
        Checks if a position exists in the positions list
        and if not creates a new key, and Position instance
        for this particular asset.
        """
        if asset in self.positions:
            position = self.positions[asset]
        else:
            position = Position(asset)
            self.positions[asset] = position
        return position