Merge branch 'codex/repro-1026' of https://github.com/PolicyEngine/policyengine-uk into codex/merge-1549

Author: MaxGhenis

policyengine_uk/tests/test_lha_freeze.py

@@ -0,0 +1,50 @@
+"""Regression tests for the LHA freeze parameter."""
+
+from policyengine_uk import Simulation
+
+
+YEAR = 2026
+
+SITUATION = {
+    "people": {
+        "person": {
+            "age": {YEAR: 30},
+            "employment_income": {YEAR: 0},
+        }
+    },
+    "benunits": {
+        "benunit": {
+            "members": ["person"],
+            "benunit_rent": {YEAR: 10_000},
+            "LHA_eligible": {YEAR: True},
+            "housing_benefit_applicable_amount": {YEAR: 11_000},
+            "housing_benefit_applicable_income": {YEAR: 11_000},
+            "housing_benefit_non_dep_deductions": {YEAR: 0},
+        }
+    },
+    "households": {
+        "household": {
+            "members": ["person"],
+            "region": {YEAR: "LONDON"},
+        }
+    },
+}
+
+
+def test_lha_freeze_changes_lha_rate_and_housing_benefit_entitlement():
+    frozen = Simulation(
+        situation=SITUATION,
+        reform={"gov.dwp.LHA.freeze": {"2026": True}},
+    )
+    unfrozen = Simulation(
+        situation=SITUATION,
+        reform={"gov.dwp.LHA.freeze": {"2026": False}},
+    )
+
+    frozen_rate = frozen.calculate("BRMA_LHA_rate", YEAR)[0]
+    unfrozen_rate = unfrozen.calculate("BRMA_LHA_rate", YEAR)[0]
+    frozen_entitlement = frozen.calculate("housing_benefit_entitlement", YEAR)[0]
+    unfrozen_entitlement = unfrozen.calculate("housing_benefit_entitlement", YEAR)[0]
+
+    assert unfrozen_rate > frozen_rate
+    assert unfrozen_entitlement > frozen_entitlement