def test_get_observable_instance():
audusd = FxRate("AUDUSD", 0.5)
instance = FxRate.get_observable_instance("AUDUSD")
assert instance is audusd
instance = FxRate.get_observable_instance("USDAUD")
assert instance is audusd
def test_get_instance():
audusd = FxRate("AUDUSD", 0.5)
instance = FxRate.get_instance("AUDUSD")
assert audusd is instance
with pytest.raises(ValueError):
FxRate.get_instance("USDAUD")
def test_fx_rate_positive():
fx = FxRate("AUDUSD", 0.65)
assert fx.rate == 0.65
fx.rate = 0.75
assert fx.rate == 0.75
with pytest.raises(ValueError):
fx.rate = -0.85
assert fx.rate == 0.75
def test_already_created():
""" Once a rate is created we must not create it again.
We don't want multiple objects with different
prices representing the same asset.
"""
audusd = FxRate("AUDUSD", 0.65)
assert audusd.rate == 0.65
with pytest.raises(ValueError):
FxRate("AUDUSD", 0.75)
assert audusd.rate == 0.65
def test_inverse_pair_creation():
""" Once we have created AUDUSD, for example,
we cannot create USDAUD.
"""
audusd = FxRate("AUDUSD", 0.5)
assert audusd.rate == 0.5
with pytest.raises(ValueError):
FxRate("AUDUSD", 0.5)
with pytest.raises(ValueError):
FxRate("USDAUD", 2.0)
def test_get_rate():
audusd = FxRate("AUDUSD", 0.5)
assert FxRate.get("AUDUSD") == 0.5
assert FxRate.get("USDAUD") == 2.0
audusd.rate = 0.8
assert FxRate.get("AUDUSD") == 0.8
assert FxRate.get("USDAUD") == 1.25
def test_fx_rate_get():
with pytest.raises(ValueError):
FxRate.get("AUDUSD") # not available
fx = FxRate("AUDUSD", 0.65)
assert FxRate.get("AUDUSD") == 0.65
fx.rate = 0.75
assert FxRate.get("AUDUSD") == 0.75
def test_observable():
audusd = FxRate("AUDUSD", 0.65)
class UsdCash:
def __init__(self):
self.local_value = 1.0
self.update_aud_value()
def update_aud_value(self):
rate = FxRate.get("AUDUSD")
self.aud_value = 1 / rate
def observable_update(self, observable):
self.update_aud_value()
usd_cash = UsdCash()
assert usd_cash.aud_value == 1 / 0.65
audusd.add_observer(usd_cash)
audusd.rate = 0.7
assert usd_cash.aud_value == 1 / 0.7
def update_aud_value(self):
rate = FxRate.get("AUDUSD")
self.aud_value = 1 / rate
def test_fx_rate_init():
fx = FxRate("AUDUSD", 0.65)
assert fx.currency_pair == "AUDUSD"
assert fx.rate == 0.65
def test_fx_currency_pair_read_only():
fx = FxRate("AUDUSD", 0.65)
with pytest.raises(AttributeError):
fx.currency_pair = "AUDAUD"