Document policyengine.py household-impact zero-return diagnosis (#1628)#1729
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Document policyengine.py household-impact zero-return diagnosis (#1628)#1729vahid-ahmadi wants to merge 1 commit into
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#1628 reported that two policyengine.py household-impact integration tests started asserting 0.0 for expected-positive tax / child-benefit values after bumping to policyengine-uk==2.88.0. Reproducing the same scenarios directly against policyengine-uk shows the model is healthy: a £50k single adult correctly returns £7,486 income tax, and a couple with one child correctly returns £1,354.60 child benefit at 2025 rates. The figures are stable across 2022-2025. So the regression is upstream in policyengine.py's test harness, not a model bug. Most likely cause: the harness depending on the model's default_input_period (2025) vs the year encoded in the test fixture, or being broken by the default-dataset env var requirement introduced since the previous 2.74 pin. Persist the diagnosis as a docs page so the next reviewer of #1628 gets a one-stop explanation. Guidance for the upstream fix: - pass explicit period= to every calculate() call, - use Microsimulation(situation=...) for single-household queries (no dataset needed), - assert against the fixture-encoded year rather than the model's default. Cross-links to mp30k-uk-switch-plan.md which documents the env-var contract this issue collides with.
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Summary
policyengine.pyhousehold-impact integration tests started asserting0.0for expected-positive tax / child-benefit values after bumping the UK extra topolicyengine-uk==2.88.0.policyengine-ukmain:income_tax = 7486.00✓child_benefit = 1354.60✓policyengine.pytest-harness regression, most likely from:default_input_period/default_calculation_perioddefaulting to 2025 (so a 2024 situation queried at the default returns 0 for unset inputs), ordocs/book/validation/policyengine-py-household-impact.mddocumenting the diagnosis from the UK side and providing guidance for the upstream fix (pass explicitperiod=, useMicrosimulation(situation=...)for single-household queries, assert against the fixture-encoded year).mp30k-uk-switch-plan.mdwhich documents the env-var contract this collides with.policyengine.py's test harness.Test plan
Microsimulation(situation=...); figures match the expected values.validation/.🤖 Generated with Claude Code