testing new features

tests/test_currency.py

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+import pytest
+
+from cashflow_model import CurrencyConverter, CurrencyError, ExchangeRate
+
+
+class TestExchangeRate:
+    def test_to_dict_roundtrip(self):
+        rate = ExchangeRate(from_currency="USD", to_currency="RUB", rate=80.0)
+        d = rate.to_dict()
+        r2 = ExchangeRate.from_dict(d)
+        assert r2.from_currency == "USD"
+        assert r2.to_currency == "RUB"
+        assert r2.rate == 80.0
+
+    def test_defaults(self):
+        r = ExchangeRate()
+        assert r.from_currency == "USD"
+        assert r.to_currency == "RUB"
+        assert r.rate == 80.0
+
+
+class TestCurrencyConverter:
+    def test_convert_usd_to_rub(self, sample_converter):
+        result = sample_converter.convert(100, "USD", "RUB")
+        assert result == 8000.0
+
+    def test_convert_rub_to_usd(self, sample_converter):
+        result = sample_converter.convert(8000, "RUB", "USD")
+        assert result == 100.0
+
+    def test_same_currency(self, sample_converter):
+        result = sample_converter.convert(500, "USD", "USD")
+        assert result == 500.0
+
+    def test_unknown_pair(self):
+        converter = CurrencyConverter()
+        with pytest.raises(CurrencyError):
+            converter.convert(100, "USD", "RUB")
+
+    def test_negative_rate(self):
+        converter = CurrencyConverter()
+        with pytest.raises(CurrencyError):
+            converter.set_rate("USD", "RUB", -1)
+
+    def test_zero_rate(self):
+        converter = CurrencyConverter()
+        with pytest.raises(CurrencyError):
+            converter.set_rate("USD", "RUB", 0)
+
+    def test_inverse_auto(self):
+        rate = ExchangeRate(from_currency="EUR", to_currency="RUB", rate=90.0)
+        converter = CurrencyConverter([rate])
+        assert converter.convert(900, "RUB", "EUR") == 10.0
+
+    def test_get_symbol(self, sample_converter):
+        assert sample_converter.get_symbol("USD") == "$"
+        assert sample_converter.get_symbol("RUB") == "₽"
+        assert sample_converter.get_symbol("XYZ") == "XYZ"
+
+    def test_with_defaults(self):
+        converter = CurrencyConverter.with_defaults()
+        assert converter.convert(10, "USD", "RUB") == 800.0
+
+    def test_multiple_rates(self):
+        rates = [
+            ExchangeRate(from_currency="USD", to_currency="RUB", rate=80.0),
+            ExchangeRate(from_currency="EUR", to_currency="RUB", rate=90.0),
+        ]
+        converter = CurrencyConverter(rates)
+        assert converter.convert(10, "USD", "RUB") == 800.0
+        assert converter.convert(10, "EUR", "RUB") == 900.0
+        assert converter.convert(900, "RUB", "EUR") == 10.0