Initial commit: Four-Quadrant Balance Sheet Matrix (FQBM) framework

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_commodity.py

@@ -0,0 +1,32 @@
+"""Tests for Sheet 6: Commodity shock channel (Part VI)."""
+
+import pytest
+from fqbm.state import FQBMState
+from fqbm.sheets.commodity import (
+    inflation_composite,
+    commodity_step,
+    CommodityParams,
+)
+
+
+def test_inflation_composite():
+    pi = inflation_composite(0.02, 0.1, 0.05, 0.1, 0.2)
+    assert pi == pytest.approx(0.02 + 0.1 * 0.1 + 0.2 * 0.05)
+    assert pi > 0.02
+
+
+def test_commodity_step():
+    state = FQBMState(O=1.0)
+    params = CommodityParams(d_O=0.1)
+    out = commodity_step(state, params)
+    assert out.O == pytest.approx(1.1)
+    params2 = CommodityParams(d_O=-0.05)
+    out2 = commodity_step(out, params2)
+    assert out2.O == pytest.approx(1.1 * 0.95)
+
+
+def test_commodity_step_zero_o():
+    state = FQBMState(O=0.0)
+    params = CommodityParams(d_O=0.1)
+    out = commodity_step(state, params)
+    assert out.O == pytest.approx(1.1)