more methods and tests

tests/tests_unit/test_exchange_rates.py

@@ -4,7 +4,12 @@ from decimal import Decimal
 from money.currency import Currency
 from money.money import Money
 
-from xexe.exchange_rates import ExchangeRate, ExchangeRates, add_equal_rates
+from xexe.exchange_rates import (
+    ExchangeRate,
+    ExchangeRates,
+    add_equal_rates,
+    add_inverse_rates,
+)
 
 
 def test_exchange_rate_creation_works():
@@ -124,6 +129,26 @@ def test_present_dates_works_fine():
     }
 
 
+def test_exchange_rates_is_rate_present_method_works_fine():
+    a_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.EUR,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2020, 3, 10),
+    )
+    another_rate = ExchangeRate(
+        from_currency=Currency.GBP,
+        to_currency=Currency.JPY,
+        rate=Decimal("10"),
+        rate_date=datetime.date(2019, 10, 3),
+    )
+
+    rates = ExchangeRates({a_rate})
+
+    assert rates.is_rate_present(a_rate)
+    assert not rates.is_rate_present(another_rate)
+
+
 def test_add_equal_rates_returns_expected_values():
     a_rate = ExchangeRate(
         from_currency=Currency.USD,
@@ -170,3 +195,73 @@ def test_add_equal_rates_runs_on_empty_rates():
     empty_rates = add_equal_rates(empty_rates)
 
     assert True
+
+
+def test_add_equal_rates_overwrites():
+    a_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.USD,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2020, 3, 10),
+    )
+
+    rates = ExchangeRates([a_rate])
+
+    assert len(rates) == 1
+
+    rates = add_equal_rates(rates, overwrite=True)
+
+    assert len(rates) == 1
+    assert list(rates)[0].amount == 1
+
+
+def test_add_equal_rates_does_not_overwrite():
+    a_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.USD,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2020, 3, 10),
+    )
+
+    rates = ExchangeRates([a_rate])
+
+    assert len(rates) == 1
+
+    rates = add_equal_rates(rates, overwrite=False)
+
+    assert len(rates) == 1
+    assert list(rates)[0].amount == Decimal("1.2")
+
+
+def test_add_inverse_rates_returns_expected():
+    a_rate = ExchangeRate(
+        from_currency=Currency.EUR,
+        to_currency=Currency.USD,
+        rate=Decimal("1.25"),
+        rate_date=datetime.date(2020, 3, 10),
+    )
+    inverse_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.EUR,
+        rate=Decimal("0.8"),
+        rate_date=datetime.date(2020, 3, 10),
+    )
+
+    rates = ExchangeRates([a_rate])
+
+    assert len(rates) == 1
+
+    rates = add_inverse_rates(rates)
+
+    assert len(rates) == 2
+
+    assert rates.is_rate_present(inverse_rate)
+    assert rates[inverse_rate.descriptor].amount == Decimal("0.8")
+
+
+def test_add_inverse_rates_runs_on_empty_rates():
+    empty_rates = ExchangeRates()
+
+    empty_rates = add_inverse_rates(empty_rates)
+
+    assert True