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

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

tests/test_matrix.py

@@ -0,0 +1,32 @@
+"""Tests for Part I: Four-quadrant matrix."""
+
+from fqbm.state import FQBMState
+from fqbm.matrix import four_quadrant_matrix, four_quadrant_summary
+
+
+def test_four_quadrant_matrix():
+    state = FQBMState(B=100, R=50, C=30, Loans=200, Deposits=180, E_cb=20, E_b=20)
+    df = four_quadrant_matrix(state)
+    assert "Assets (Dr)" in df.columns
+    assert "Liabilities (Dr)" in df.columns
+    assert "Liabilities (Cr)" in df.columns
+    last = df.iloc[-1]
+    assert float(last["Assets (Dr)"]) == 300
+    assert float(last["Liabilities (Cr)"]) == 40
+
+
+def test_four_quadrant_matrix_with_L_cb():
+    state = FQBMState(B=80, R=40, C=20, Loans=100, Deposits=90, E_cb=20, E_b=10)
+    df = four_quadrant_matrix(state, L_cb=10)
+    last = df.iloc[-1]
+    assert float(last["Assets (Dr)"]) == 190
+
+
+def test_four_quadrant_summary_identity():
+    state = FQBMState(B=50, R=30, C=10, Loans=100, Deposits=95, E_cb=10, E_b=5)
+    s = four_quadrant_summary(state)
+    assert "total_assets_dr" in s
+    assert "identity_A_eq_L_plus_E" in s
+    assert s["total_assets_dr"] == 150
+    assert s["total_liabilities_dr"] + s["total_liabilities_cr"] == 150
+    assert s["identity_A_eq_L_plus_E"] is True