Fix program registry model references

changelog.d/2116.fixed.md

@@ -0,0 +1 @@
+- Corrected the JSA, ESA and DLA program registry variable mappings, narrowed Benefit Cap's parameter prefix to its own subtree, removed Maternity Allowance's unrelated DWP parameter prefix, and added validation of all declared registry variables and parameter prefixes.

policyengine_uk/programs.yaml

@@ -249,7 +249,7 @@ programs:
     agency: DWP
     status: complete
     coverage: UK
-    variable: JSA
+    variable: jsa
     parameter_prefix: gov.dwp.JSA
     verified_start_year: 2022
     notes: Income-based and contribution-based
@@ -261,7 +261,7 @@ programs:
     agency: DWP
     status: complete
     coverage: UK
-    variable: ESA
+    variable: esa
     parameter_prefix: gov.dwp.ESA
     verified_start_year: 2022
     notes: Income-related and contribution-based
@@ -296,7 +296,7 @@ programs:
     agency: DWP
     status: complete
     coverage: UK
-    variable: DLA
+    variable: dla
     parameter_prefix: gov.dwp.dla
     verified_start_year: 2022
 
@@ -319,7 +319,7 @@ programs:
     status: complete
     coverage: UK
     variable: benefit_cap_reduction
-    parameter_prefix: gov.dwp
+    parameter_prefix: gov.dwp.benefit_cap
     verified_start_year: 2022
     notes: Universal Credit (uc_benefit_cap) and Housing Benefit (housing_benefit_benefit_cap) each apply their own cap; benefit_cap_reduction is the sum of their reductions
 
@@ -377,7 +377,6 @@ programs:
     status: complete
     coverage: UK
     variable: maternity_allowance
-    parameter_prefix: gov.dwp
     verified_start_year: 2022
 
   # --- DfE programs ---

policyengine_uk/tests/test_program_registry.py

@@ -0,0 +1,56 @@
+"""Keep the public program registry linked to real model objects."""
+
+import pytest
+import yaml
+from policyengine_core.parameters import ParameterNode
+
+from policyengine_uk import CountryTaxBenefitSystem
+
+PROGRAMS = yaml.safe_load(CountryTaxBenefitSystem.modelled_policies.read_text())[
+    "programs"
+]
+
+
+@pytest.fixture(scope="module")
+def tax_benefit_system():
+    return CountryTaxBenefitSystem()
+
+
+@pytest.mark.parametrize(
+    "program", [p for p in PROGRAMS if "variable" in p], ids=lambda p: p["id"]
+)
+def test_program_variables_exist(program, tax_benefit_system):
+    assert program["variable"] in tax_benefit_system.variables, (
+        f"{program['id']} references unknown variable {program['variable']!r}"
+    )
+
+
+@pytest.mark.parametrize(
+    "program", [p for p in PROGRAMS if "parameter_prefix" in p], ids=lambda p: p["id"]
+)
+def test_program_parameter_prefixes_exist(program, tax_benefit_system):
+    prefix = program["parameter_prefix"]
+    assert isinstance(tax_benefit_system.parameters.get_child(prefix), ParameterNode), (
+        f"{program['id']} parameter prefix {prefix!r} does not name a parameter node"
+    )
+
+
+def test_maternity_allowance_does_not_advertise_unrelated_parameters():
+    """Reported Maternity Allowance has no policy parameter subtree (#2116)."""
+    program = next(p for p in PROGRAMS if p["id"] == "maternity_allowance")
+    assert "parameter_prefix" not in program
+
+
+def test_benefit_cap_does_not_advertise_unrelated_parameters(tax_benefit_system):
+    """The advertised Benefit Cap subtree excludes other DWP programs (#2116)."""
+    program = next(p for p in PROGRAMS if p["id"] == "benefit_cap")
+    advertised = tax_benefit_system.parameters.get_child(program["parameter_prefix"])
+    benefit_cap = tax_benefit_system.parameters.gov.dwp.benefit_cap
+
+    assert "universal_credit" not in advertised.children
+    assert "JSA" not in advertised.children
+    assert advertised.get_child("single.in_london") is benefit_cap.single.in_london
+    assert (
+        advertised.get_child("non_single.outside_london")
+        is benefit_cap.non_single.outside_london
+    )