feat: Enhance currency handling and validation across scenarios

- Updated form template to prefill currency input with default value and added help text for clarity.
- Modified integration tests to assert more descriptive error messages for invalid currency codes.
- Introduced new tests for currency normalization and validation in various scenarios, including imports and exports.
- Added comprehensive tests for pricing calculations, ensuring defaults are respected and overrides function correctly.
- Implemented unit tests for pricing settings repository, ensuring CRUD operations and default settings are handled properly.
- Enhanced scenario pricing evaluation tests to validate currency handling and metadata defaults.
- Added simulation tests to ensure Monte Carlo runs are accurate and handle various distribution scenarios.

tests/test_pricing_settings_repository.py

@@ -0,0 +1,209 @@
+from __future__ import annotations
+
+from collections.abc import Iterator
+
+import pytest
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+
+from config.database import Base
+from models import PricingImpuritySettings, PricingMetalSettings, PricingSettings
+from services.pricing import PricingMetadata
+from services.repositories import (
+    PricingSettingsRepository,
+    ensure_default_pricing_settings,
+)
+from services.unit_of_work import UnitOfWork
+
+
+@pytest.fixture()
+def engine() -> Iterator:
+    engine = create_engine("sqlite:///:memory:", future=True)
+    Base.metadata.create_all(bind=engine)
+    try:
+        yield engine
+    finally:
+        Base.metadata.drop_all(bind=engine)
+
+
+@pytest.fixture()
+def session(engine) -> Iterator[Session]:
+    TestingSession = sessionmaker(
+        bind=engine, expire_on_commit=False, future=True)
+    db = TestingSession()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+def test_pricing_settings_repository_crud(session: Session) -> None:
+    repo = PricingSettingsRepository(session)
+
+    settings = PricingSettings(
+        name="Contract A",
+        slug="Contract-A",
+        default_currency="usd",
+        default_payable_pct=95.0,
+        moisture_threshold_pct=7.5,
+        moisture_penalty_per_pct=1500.0,
+    )
+    repo.create(settings)
+
+    metal_override = PricingMetalSettings(
+        metal_code="Copper",
+        payable_pct=96.0,
+        moisture_threshold_pct=None,
+        moisture_penalty_per_pct=None,
+    )
+    repo.attach_metal_override(settings, metal_override)
+
+    impurity_override = PricingImpuritySettings(
+        impurity_code="as",
+        threshold_ppm=100.0,
+        penalty_per_ppm=3.5,
+    )
+    repo.attach_impurity_override(settings, impurity_override)
+
+    retrieved = repo.get_by_slug("CONTRACT-A", include_children=True)
+    assert retrieved.slug == "contract-a"
+    assert retrieved.default_currency == "USD"
+    assert len(retrieved.metal_overrides) == 1
+    assert retrieved.metal_overrides[0].metal_code == "copper"
+    assert len(retrieved.impurity_overrides) == 1
+    assert retrieved.impurity_overrides[0].impurity_code == "AS"
+
+    listed = repo.list(include_children=True)
+    assert len(listed) == 1
+    assert listed[0].id == settings.id
+
+
+def test_ensure_default_pricing_settings_creates_and_updates(session: Session) -> None:
+    repo = PricingSettingsRepository(session)
+
+    metadata_initial = PricingMetadata(
+        default_payable_pct=100.0,
+        default_currency="USD",
+        moisture_threshold_pct=8.0,
+        moisture_penalty_per_pct=0.0,
+        impurity_thresholds={"As": 50.0},
+        impurity_penalty_per_ppm={"As": 2.0},
+    )
+
+    result_create = ensure_default_pricing_settings(
+        repo,
+        metadata=metadata_initial,
+        name="Seeded Pricing",
+        description="Seeded from defaults",
+    )
+
+    assert result_create.created is True
+    assert result_create.settings.slug == "default"
+    assert result_create.settings.default_currency == "USD"
+    assert len(result_create.settings.impurity_overrides) == 1
+    assert result_create.settings.impurity_overrides[0].penalty_per_ppm == 2.0
+
+    metadata_update = PricingMetadata(
+        default_payable_pct=97.0,
+        default_currency="EUR",
+        moisture_threshold_pct=6.5,
+        moisture_penalty_per_pct=250.0,
+        impurity_thresholds={"As": 45.0, "Pb": 12.0},
+        impurity_penalty_per_ppm={"As": 3.0, "Pb": 1.25},
+    )
+
+    result_update = ensure_default_pricing_settings(
+        repo,
+        metadata=metadata_update,
+        name="Seeded Pricing",
+        description="Seeded from defaults",
+    )
+
+    assert result_update.created is False
+    assert result_update.updated_fields > 0
+    assert result_update.impurity_upserts >= 1
+
+    updated = repo.get_by_slug("default", include_children=True)
+    assert updated.default_currency == "EUR"
+    as_override = {
+        item.impurity_code: item for item in updated.impurity_overrides}["AS"]
+    assert float(as_override.threshold_ppm) == 45.0
+    assert float(as_override.penalty_per_ppm) == 3.0
+    pb_override = {
+        item.impurity_code: item for item in updated.impurity_overrides}["PB"]
+    assert float(pb_override.threshold_ppm) == 12.0
+
+
+def test_unit_of_work_exposes_pricing_settings(engine) -> None:
+    TestingSession = sessionmaker(
+        bind=engine, expire_on_commit=False, future=True)
+    metadata = PricingMetadata(
+        default_payable_pct=99.0,
+        default_currency="USD",
+        moisture_threshold_pct=7.0,
+        moisture_penalty_per_pct=125.0,
+        impurity_thresholds={"Zn": 80.0},
+        impurity_penalty_per_ppm={"Zn": 0.5},
+    )
+
+    with UnitOfWork(session_factory=TestingSession) as uow:
+        assert uow.pricing_settings is not None
+        result = uow.ensure_default_pricing_settings(
+            metadata=metadata,
+            slug="contract-core",
+            name="Contract Core",
+        )
+        assert result.settings.slug == "contract-core"
+        assert result.created is True
+
+    with UnitOfWork(session_factory=TestingSession) as uow:
+        assert uow.pricing_settings is not None
+        stored = uow.pricing_settings.get_by_slug(
+            "contract-core", include_children=True)
+        assert stored.default_payable_pct == 99.0
+        assert stored.impurity_overrides[0].impurity_code == "ZN"
+
+
+def test_unit_of_work_get_pricing_metadata_returns_defaults(engine) -> None:
+    TestingSession = sessionmaker(
+        bind=engine, expire_on_commit=False, future=True)
+    seeded_metadata = PricingMetadata(
+        default_payable_pct=96.5,
+        default_currency="aud",
+        moisture_threshold_pct=6.25,
+        moisture_penalty_per_pct=210.0,
+        impurity_thresholds={"As": 45.0, "Pb": 15.0},
+        impurity_penalty_per_ppm={"As": 1.75, "Pb": 0.9},
+    )
+
+    with UnitOfWork(session_factory=TestingSession) as uow:
+        result = uow.ensure_default_pricing_settings(
+            metadata=seeded_metadata,
+            slug="default",
+            name="Default Contract",
+            description="Primary contract defaults",
+        )
+        assert result.created is True
+
+    with UnitOfWork(session_factory=TestingSession) as uow:
+        retrieved = uow.get_pricing_metadata()
+
+    assert retrieved is not None
+    assert retrieved.default_currency == "AUD"
+    assert retrieved.default_payable_pct == 96.5
+    assert retrieved.moisture_threshold_pct == 6.25
+    assert retrieved.moisture_penalty_per_pct == 210.0
+    assert retrieved.impurity_thresholds["AS"] == 45.0
+    assert retrieved.impurity_thresholds["PB"] == 15.0
+    assert retrieved.impurity_penalty_per_ppm["AS"] == 1.75
+    assert retrieved.impurity_penalty_per_ppm["PB"] == 0.9
+
+
+def test_unit_of_work_get_pricing_metadata_returns_none_when_missing(engine) -> None:
+    TestingSession = sessionmaker(
+        bind=engine, expire_on_commit=False, future=True)
+
+    with UnitOfWork(session_factory=TestingSession) as uow:
+        missing = uow.get_pricing_metadata(slug="non-existent")
+
+    assert missing is None