tests and small refactors for exchange rates

tests/tests_unit/test_exchange_rates.py

@@ -0,0 +1,172 @@
+import datetime
+from decimal import Decimal
+
+from money.currency import Currency
+from money.money import Money
+
+from xexe.exchange_rates import ExchangeRate, ExchangeRates, add_equal_rates
+
+
+def test_exchange_rate_creation_works():
+
+    a_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.EUR,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date.today(),
+    )
+
+    assert a_rate.from_currency.value == "USD"
+    assert a_rate.to_currency.value == "EUR"
+    assert a_rate.rate.amount == Decimal("1.2")
+    assert a_rate.rate_date == datetime.date.today()
+
+
+def test_descriptor_builds_properly():
+
+    a_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.EUR,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2020, 3, 10),
+    )
+
+    assert a_rate.descriptor == "USDEUR2020-03-10"
+
+
+def test_exchange_rates_builds_index_properly():
+
+    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),
+    )
+    a_third_rate = ExchangeRate(
+        from_currency=Currency.NZD,
+        to_currency=Currency.PLN,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2025, 1, 10),
+    )
+
+    rates = ExchangeRates({a_rate, another_rate, a_third_rate})
+
+    assert len(rates._rate_index) == 3
+    assert "USDEUR2020-03-10" in rates._rate_index
+    assert "GBPJPY2019-10-03" in rates._rate_index
+    assert "NZDPLN2025-01-10" in rates._rate_index
+
+
+def test_present_currencies_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),
+    )
+    a_third_rate = ExchangeRate(
+        from_currency=Currency.NZD,
+        to_currency=Currency.PLN,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2025, 1, 10),
+    )
+
+    rates = ExchangeRates({a_rate, another_rate, a_third_rate})
+
+    assert rates.present_currencies == {
+        Currency.USD,
+        Currency.EUR,
+        Currency.JPY,
+        Currency.GBP,
+        Currency.NZD,
+        Currency.PLN,
+    }
+
+
+def test_present_dates_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),
+    )
+    a_third_rate = ExchangeRate(
+        from_currency=Currency.NZD,
+        to_currency=Currency.PLN,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2025, 1, 10),
+    )
+
+    rates = ExchangeRates({a_rate, another_rate, a_third_rate})
+
+    assert rates.present_dates == {
+        datetime.date(2025, 1, 10),
+        datetime.date(2019, 10, 3),
+        datetime.date(2020, 3, 10),
+    }
+
+
+def test_add_equal_rates_returns_expected_values():
+    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),
+    )
+    a_third_rate = ExchangeRate(
+        from_currency=Currency.NZD,
+        to_currency=Currency.PLN,
+        rate=Decimal("1.2"),
+        rate_date=datetime.date(2025, 1, 10),
+    )
+
+    rates = ExchangeRates({a_rate, another_rate, a_third_rate})
+
+    assert len(rates) == 3
+
+    rates = add_equal_rates(rates)
+
+    equal_rate_entry_count = len(list(rates.present_currencies)) * len(
+        rates.present_dates
+    )
+    assert len(rates) == equal_rate_entry_count + 3
+    assert (
+        len([rate for rate in rates if rate.from_currency == rate.to_currency])
+        == equal_rate_entry_count
+    )
+    for rate in rates:
+        if rate.from_currency == rate.to_currency:
+            assert rate.amount == Decimal(1)
+
+
+def test_add_equal_rates_runs_on_empty_rates():
+
+    empty_rates = ExchangeRates()
+
+    empty_rates = add_equal_rates(empty_rates)
+
+    assert True