Model/backend/tests/test_funding.py

import pytest
import pandas as pd
from backend.Funding import Funding, EligibilityCaveats


@pytest.fixture
def mock_project_scores_matrix():
    data = []
    floor_segments = ["0-72", "73-97", "98-199", "200"]
    starting_bands = ["Low_G", "High_G", "Low_F", "High_F", "Low_E", "High_E", "Low_D", "High_D", "Low_C", "High_C"]
    finishing_bands = ["Low_C", "High_C", "Low_B"]  # covers likely improvement targets

    cost = 50.0
    for floor in floor_segments:
        for start in starting_bands:
            for finish in finishing_bands:
                if start != finish:  # skip identical start/finish (no SAP movement)
                    data.append({
                        "Floor Area Segment": floor,
                        "Starting Band": start,
                        "Finishing Band": finish,
                        "Cost Savings": cost
                    })
                    cost += 5.0  # increment to create variety

    return pd.DataFrame(data)


@pytest.fixture
def mock_partial_scores_matrix():
    return pd.DataFrame([{"dummy": "data"}])  # not used for eligibility tests yet


@pytest.fixture
def mock_whlg_postcodes():
    return pd.DataFrame([{"Postcode": "ab12cd"}])


### -------------------------
### PRIVATE RENTED SECTOR (PRS)
### -------------------------

def test_eco4_prs_eligible_with_swi(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Private",
    )

    # The property is:
    # 1) private,
    # 2) EPC E
    # 3) is getting a solid was measure
    # so it's eligible for ECO4

    measures = [{"type": "internal_wall_insulation", "is_innovation": False}]
    funding.check_funding(
        measures=measures,
        starting_sap=50,  # EPC E
        ending_sap=69,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True,
        council_tax_band="B"
    )

    assert funding.eco4_eligible
    assert EligibilityCaveats.TENANT_ON_BENEFITS_OR_LOW_INCOME in funding.eco4_eligibility_caveats


def test_eco4_prs_not_eligible_high_epc(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    """Should NOT be eligible if EPC is too high (C or above)."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Private",
    )

    measures = [{"type": "internal_wall_insulation", "is_innovation": False}]
    funding.check_funding(
        measures=measures,
        starting_sap=72,  # EPC C (too high)
        ending_sap=75,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True,
        council_tax_band="B"
    )

    assert not funding.eco4_eligible


def test_gbis_prs_general_eligibility(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    """PRS EPC D–G & council tax band A–D should trigger GBIS general route."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Private",
    )

    measures = [{"type": "internal_wall_insulation", "is_innovation": False}]
    funding.check_funding(
        measures=measures,
        starting_sap=65,  # EPC D
        ending_sap=70,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True,
        council_tax_band="A"
    )

    assert funding.gbis_eligible


def test_gbis_prs_low_income_caveat(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    """PRS EPC D–G should flag low-income caveat when low-income route is used."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Private",
    )

    measures = [{"type": "cavity_wall_insulation", "is_innovation": False}]
    funding.check_funding(
        measures=measures,
        starting_sap=60,  # EPC D
        ending_sap=70,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True,
        council_tax_band="B"
    )

    assert funding.gbis_eligible
    assert EligibilityCaveats.TENANT_ON_BENEFITS_OR_LOW_INCOME in funding.gbis_eligibility_caveats


### -------------------------
### SOCIAL HOUSING
### -------------------------

def test_eco4_sh_epc_e_eligible(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    """EPC E social housing should be ECO4 eligible without innovation."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Social",
    )

    measures = [{"type": "internal_wall_insulation", "is_innovation": False}]
    funding.check_funding(
        measures=measures,
        starting_sap=50,  # EPC E
        ending_sap=69,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True
    )

    assert funding.eco4_eligible


def test_eco4_sh_epc_d_requires_innovation(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    """EPC D social housing should require an innovation measure."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Social",
    )

    measures = [{"type": "internal_wall_insulation", "is_innovation": False}]
    funding.check_funding(
        measures=measures,
        starting_sap=60,  # EPC D
        ending_sap=69,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True
    )

    assert not funding.eco4_eligible
    assert EligibilityCaveats.INNOVATION_REQUIRED in funding.eco4_eligibility_caveats


def test_eco4_sh_solar_pv_requires_heating(mock_project_scores_matrix, mock_partial_scores_matrix, mock_whlg_postcodes):
    """Solar PV as innovation measure requires ASHP or HHRSH."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Social",
    )

    measures = [{"type": "solar_pv", "is_innovation": True}]
    funding.check_funding(
        measures=measures,
        starting_sap=60,  # EPC D
        ending_sap=69,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True
    )

    assert not funding.eco4_eligible
    assert EligibilityCaveats.SOLAR_NEEDS_HEATING in funding.eco4_eligibility_caveats


def test_eco4_sh_solar_pv_with_heating_is_ok(mock_project_scores_matrix, mock_partial_scores_matrix,
                                             mock_whlg_postcodes):
    """Solar PV innovation with ASHP should pass EPC D innovation rule."""
    funding = Funding(
        project_scores_matrix=mock_project_scores_matrix,
        partial_project_scores_matrix=mock_partial_scores_matrix,
        whlg_eligible_postcodes=mock_whlg_postcodes,
        social_cavity_abs_rate=13.5,
        social_solid_abs_rate=17,
        private_cavity_abs_rate=13.5,
        private_solid_abs_rate=17,
        tenure="Social",
    )

    measures = [
        {"type": "solar_pv", "is_innovation": True},
        {"type": "air_source_heat_pump", "is_innovation": False}
    ]
    funding.check_funding(
        measures=measures,
        starting_sap=60,  # EPC D
        ending_sap=69,
        floor_area=80,
        mainheat_description="Boiler and radiators, mains gas",
        heating_control_description="Programmer, room thermostat and TRVs",
        is_cavity=True
    )

    assert funding.eco4_eligible
    assert EligibilityCaveats.SOLAR_NEEDS_HEATING not in funding.eco4_eligibility_caveats