intial impelmentation of strategic optimiser with tests

asset_list/app.py

@@ -73,61 +73,24 @@ def app():
     Property UPRN
     """
 
-    data_folder = "/Users/khalimconn-kowlessar/Documents/hestia/Customers/West Kent"
+    data_folder = "/Users/khalimconn-kowlessar/Downloads"
-    data_filename = "West Kent Asset List.xlsx"
+    data_filename = "assests.xlsx"
     sheet_name = "Sheet1"
-    postcode_column = "POSTCODE"
+    postcode_column = "Postcode"
-    address1_column = None
+    address1_column = "Address"
     address1_method = "house_number_extraction"
-    fulladdress_column = "ADDRESS"
+    fulladdress_column = None
-    address_cols_to_concat = []
+    address_cols_to_concat = ["Address"]
     missing_postcodes_method = None
     landlord_year_built = None
-    landlord_os_uprn = None
+    landlord_os_uprn = "UPRN"
-    landlord_property_type = "PROPERTY TYPE"
+    landlord_property_type = "Archetype"
-    landlord_built_form = None
+    landlord_built_form = "Bedroom Count"
-    landlord_wall_construction = "wall combined"
+    landlord_wall_construction = "Wall Insulation Type"
-    landlord_roof_construction = "HEATING SYSTEM"
+    landlord_roof_construction = "Roof Type"
-    landlord_heating_system = None
+    landlord_heating_system = "Boiler Type"
     landlord_existing_pv = None
-    landlord_property_id = "UPRN"
+    landlord_property_id = "Tab"
-    landlord_sap = None
-    outcomes_filename = None
-    outcomes_sheetname = None
-    outcomes_postcode = None
-    outcomes_houseno = None
-    outcomes_id = None
-    outcomes_address = None
-    master_filepaths = []
-    master_id_colnames = []
-    master_to_asset_list_filepath = None
-    phase = False
-    ecosurv_landlords = None
-    asset_list_header = 0
-    landlord_block_reference = None
-
-    # Peabody data for cleaning
-    data_folder = (
-        "/Users/khalimconn-kowlessar/Documents/hestia/Customers/Peabody/Nov 2025 Consulting "
-        "Project/data_validation"
-    )
-    data_filename = "to_standardise_uprns.xlsx"
-    sheet_name = "Sheet1"
-    postcode_column = "POSTCODE"
-    address1_column = None
-    address1_method = "house_number_extraction"
-    fulladdress_column = "ADDRESS"
-    address_cols_to_concat = []
-    missing_postcodes_method = None
-    landlord_year_built = None
-    landlord_os_uprn = None
-    landlord_property_type = "PROPERTY TYPE"
-    landlord_built_form = None  # Skipped as empty
-    landlord_wall_construction = "wall combined"  # combin F + G
-    landlord_roof_construction = "HEATING SYSTEM"  # Combine I + J
-    landlord_heating_system = None  # Check with Khalim
-    landlord_existing_pv = None
-    landlord_property_id = "UPRN"
     landlord_sap = None
     outcomes_filename = None
     outcomes_sheetname = None
@@ -279,7 +242,7 @@ def app():
         if skip is not None and not force_retrieve_data:
             if i <= skip:
                 continue
-        chunk = asset_list.standardised_asset_list[i : i + chunk_size]
+        chunk = asset_list.standardised_asset_list[i: i + chunk_size]
         epc_data_chunk, errors_chunk, no_epc_chunk = get_data(
             df=chunk,
             row_id_name=asset_list.DOMNA_PROPERTY_ID,
@@ -422,7 +385,7 @@ def app():
     # Retrieve just the data we need
     epc_df = epc_df[
         [asset_list.DOMNA_PROPERTY_ID] + list(asset_list.EPC_API_DATA_NAMES.keys())
-    ].rename(columns=asset_list.EPC_API_DATA_NAMES)
+        ].rename(columns=asset_list.EPC_API_DATA_NAMES)
 
     # Look for columns not in the find my EPC data, which will have happened if we didn't
     # retrieve it in the first place
@@ -439,7 +402,7 @@ def app():
         find_my_epc_data[
             [asset_list.DOMNA_PROPERTY_ID, "epc_has_floor_recommendation"]
             + list(asset_list.FIND_EPC_DATA_NAMES.keys())
-        ].rename(columns=asset_list.FIND_EPC_DATA_NAMES),
+            ].rename(columns=asset_list.FIND_EPC_DATA_NAMES),
         how="left",
         on=asset_list.DOMNA_PROPERTY_ID,
     )

backend/engine/engine.py

@@ -1118,6 +1118,28 @@ async def model_engine(body: PlanTriggerRequest):
             # When the goal is Increasing EPC, we can run the funding optimiser
             if body.goal == "Increasing EPC":
 
+                solutions_no_budget = optimise_with_scenarios(
+                    p=p,
+                    input_measures=input_measures,
+                    budget=None,
+                    target_gain=gain,
+                    enforce_heat_pump_insulation=True,
+                    enforce_fabric_first=body.enforce_fabric_first,
+                    already_installed_sap=already_installed_sap,  # To be passed to output
+                )
+                solutions_no_budget["total_cost"]
+
+                solutions_with_budget = optimise_with_scenarios(
+                    p=p,
+                    input_measures=input_measures,
+                    budget=5000,
+                    target_gain=gain,
+                    enforce_heat_pump_insulation=True,
+                    enforce_fabric_first=body.enforce_fabric_first,
+                    already_installed_sap=already_installed_sap,  # To be passed to output
+                )
+                solutions_with_budget["total_cost"]
+
                 solutions = optimise_with_scenarios(
                     p=p,
                     input_measures=input_measures,

recommendations/optimiser/CostOptimiser.py

@@ -12,13 +12,16 @@ class CostOptimiser:
     # We add an optional buffer to the minimum gain to allow for slack in the optimisation
     BUFFER = 0.2
 
-    def __init__(self, components, min_gain, verbose=False):
+    def __init__(
+        self, components, min_gain, verbose=False, allow_slack=True
+    ):
         self.components = components
         self.min_gain = min_gain
         self.gain_constraint = None
         self.m = None
         self.variables = []
         self.solution = []
+        self.allow_slack = allow_slack
 
         self.solution_cost = None
         self.solution_gain = None
@@ -81,6 +84,20 @@ class CostOptimiser:
         for group_vars in self.variables:
             self.m += xsum(var for var in group_vars) <= 1
 
+    def add_budget_constraint(self, budget: int | float) -> None:
+        # Inject budget constraint, which ensures that sum of cost_ig * x_ig <= budget, where cost_ig represents the
+        # cost for the ith component in group g, and x_ig is the binary decision variable for the ith component in 
+        # group g
+
+        self.m += (
+            xsum(
+                item["cost"] * var
+                for group, group_vars in zip(self.components, self.variables)
+                for item, var in zip(group, group_vars)
+            )
+            <= budget
+        )
+
     def setup_slack(self):
 
         # Remove the original gain constraint
@@ -109,10 +126,17 @@ class CostOptimiser:
         self.m.optimize()
 
         if self.m.status == OptimizationStatus.INFEASIBLE:
-            # Turn off logging - too noisy
+            if self.allow_slack:
-            # logger.info("We have an infeasible model, setting up slack model")
+                self.setup_slack()
-            self.setup_slack()
+                self.m.optimize()
-            self.m.optimize()
+            else:
+                # Explicity return an empty solution
+                self.solution = []
+                self.solution_cost = 0
+                self.solution_gain = 0
+                return
+
+        # If we still have an infeasible solution, we return an empty solution
 
         self.solution = [
             item for group, group_vars in zip(self.components, self.variables) for item, var in zip(group, group_vars)

recommendations/optimiser/GainOptimiser.py

@@ -21,8 +21,8 @@ class GainOptimiser:
         :param components: List of components, where each component is a dictionary with keys "id", "cost" and "gain"
         :param max_cost: Maximum cost constraint
         :param max_gain: Maximum gain constraint
-        :param allow_slack: If True, allows the model to use slack variables to relax the cost constraint if the model
+        :param allow_slack: If True, and the solution is infeasible, allows the model to use slack variables to relax
-                            is infeasible. Defaults to True.
+                            the cost constraint if the model. Defaults to True.
         :param verbose: If True, enables verbose logging
         """
         self.components = components
@@ -86,6 +86,9 @@ class GainOptimiser:
         for group_vars in self.variables:
             self.m += xsum(var for var in group_vars) <= 1
 
+        self.m.max_gap = 0
+        self.m.integer_tol = 1e-9
+
     def setup_slack(self):
         # Remove the original cost constraint
         self.m.remove(self.cost_constraint)
@@ -148,5 +151,5 @@ class GainOptimiser:
 
         self.solution = solution
 
-        self.solution_gain = self.m.objective.x
+        self.solution_gain = sum(component['gain'] for component in self.solution)
         self.solution_cost = sum([component['cost'] for component in self.solution])

recommendations/optimiser/StrategicOptimiser.py

@@ -0,0 +1,175 @@
+from enum import Enum
+from mip import OptimizationStatus
+from typing import Sequence, Optional, TypedDict, List
+from recommendations.optimiser.CostOptimiser import CostOptimiser
+from recommendations.optimiser.GainOptimiser import GainOptimiser
+
+
+class Measure(TypedDict):
+    id: str
+    cost: float
+    gain: float
+
+
+class Strategies(Enum):
+    CASE_1_TRY_MIN_COST_WITH_CONSTRAINTS = "case_1_try_min_cost_with_constraints"
+    CASE_1_SOLVE_MAX_GAIN_UNDER_BUDGET = "case_1_solve_max_gain_under_budget"
+    CASE_2_SOLVE_MAX_GAIN_UNDER_BUDGET = "case_2_solve_max_gain_under_budget"
+    CASE_3_SOLVE_MIN_COST_FOR_TARGET = "case_3_solve_min_cost_for_target"
+
+
+class StrategicOptimiser:
+    """
+    Domain-level optimiser implementing logical optimisation logic.
+
+    Behaviour:
+
+    1) If both budget and target_gain are provided:
+        - Minimise cost subject to:
+            gain >= target_gain
+            cost <= budget
+        - If infeasible:
+            maximise gain subject to cost <= budget
+
+    2) If only budget is provided:
+        - Maximise gain under budget
+
+    3) If only target_gain is provided:
+        - Minimise cost to achieve gain
+
+    """
+
+    def __init__(
+        self,
+        components: Sequence[Sequence[Measure]],
+        budget: Optional[float] = None,
+        target_gain: Optional[float] = None,
+        verbose: bool = False,
+    ) -> None:
+
+        if not components:
+            raise ValueError("Components cannot be empty.")
+
+        if budget is None and target_gain is None:
+            raise ValueError("At least one of budget or target_gain must be provided.")
+
+        self.components = components
+        self.budget = budget
+        self.target_gain = target_gain
+        self.verbose = verbose
+
+        self.solution: List[Measure] = []
+        self.solution_cost: float = 0.0
+        self.solution_gain: float = 0.0
+
+        # For debugging purposes, we keep a record of which option was selected
+        self.strategy_used: Optional[Strategies] = None
+
+    def solve(self) -> None:
+        """
+        Primary entry point for solving the optimisation problem based on the provided budget and target gain.
+        :return:
+        """
+
+        # Case 1: budget + target
+        if self.budget is not None and self.target_gain is not None:
+            # Given:
+            # Budget B
+            # Target gain G
+            #
+            # We want the solution to:
+            #
+            # Primary problem (P1)
+            # min cost
+            # subject to
+            #
+            # gain >= 𝐺
+            # cost <= B
+            # multiple-choice constraints
+            #
+            # If (P1) is feasible → that solution is exactly what you want.
+            # If (P1) is infeasible → solve the following problem (P2):
+            #
+            # max gain
+            # subject to
+            #
+            # cost <= B
+            if self._try_min_cost_with_constraints():
+                # Keep a record of the strategy used to solve the problem, for debugging purposes
+                self.strategy_used = Strategies.CASE_1_TRY_MIN_COST_WITH_CONSTRAINTS
+                return
+            self._solve_max_gain_under_budget()
+            self.strategy_used = Strategies.CASE_1_SOLVE_MAX_GAIN_UNDER_BUDGET
+            return
+
+        # Case 2: budget only
+        if self.budget is not None:
+            self._solve_max_gain_under_budget()
+            self.strategy_used = Strategies.CASE_2_SOLVE_MAX_GAIN_UNDER_BUDGET
+            return
+
+        # Case 3: target only
+        self._solve_min_cost_for_target()
+        self.strategy_used = Strategies.CASE_3_SOLVE_MIN_COST_FOR_TARGET
+        return
+
+    # ---------------------------------------------------------
+    # Internal Functions
+    # ---------------------------------------------------------
+
+    def _try_min_cost_with_constraints(self) -> bool:
+        """
+        Try to minimise cost while satisfying:
+            gain >= target_gain
+            cost <= budget
+        """
+
+        opt = CostOptimiser(
+            self.components,
+            min_gain=self.target_gain,
+            verbose=self.verbose,
+            allow_slack=False
+        )
+
+        opt.setup()
+        opt.add_budget_constraint(self.budget)
+        opt.solve()
+
+        if opt.m.status == OptimizationStatus.INFEASIBLE:
+            return False
+
+        self._store_solution(opt.solution)
+        return True
+
+    def _solve_max_gain_under_budget(self) -> None:
+
+        opt = GainOptimiser(
+            self.components,
+            max_cost=self.budget,
+            max_gain=None,
+            allow_slack=False,
+            verbose=self.verbose
+        )
+
+        opt.setup()
+        opt.solve()
+
+        self._store_solution(opt.solution)
+
+    def _solve_min_cost_for_target(self) -> None:
+
+        opt = CostOptimiser(
+            self.components,
+            min_gain=self.target_gain,
+            verbose=self.verbose
+        )
+
+        opt.setup()
+        opt.solve()
+
+        self._store_solution(opt.solution)
+
+    def _store_solution(self, solution: List[Measure]) -> None:
+        self.solution = solution
+        self.solution_cost = sum(m["cost"] for m in solution)
+        self.solution_gain = sum(m["gain"] for m in solution)

recommendations/optimiser/funding_optimiser.py

@@ -1119,6 +1119,7 @@ def run_optimizer(
         return None, 0.0, 0.0
 
     if budget is not None:
+
         opt = GainOptimiser(
             input_measures, max_cost=budget, max_gain=0 if sub_target_gain == 0 else (sub_target_gain or float("inf")),
             allow_slack=allow_slack

recommendations/tests/test_optimiser_functions.py

@@ -5,6 +5,7 @@ from recommendations.tests.test_data.measures_to_optimise import measures_to_opt
 from recommendations.optimiser import optimiser_functions
 from recommendations.optimiser.GainOptimiser import GainOptimiser
 from recommendations.optimiser.CostOptimiser import CostOptimiser
+from recommendations.optimiser.StrategicOptimiser import StrategicOptimiser, Strategies
 
 
 class TestPrepareInputMeasures:
@@ -287,3 +288,728 @@ class TestIncreasingEpcE2e:
         # We don't add ventilation as major insulation work isn't done
         ventilation_added = any(rec["recommendation_id"] == "3_phase=2" and rec["default"] for rec in flattened)
         assert not ventilation_added, "Ventilation should not be added without major insulation work"
+
+
+class TestStrategicOptimiser:
+    def test_budget_and_target_gain(self):
+        components = [
+            [
+                {'id': '0_phase=0', 'cost': 819.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 819.0, 'raw_cost': 819.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '1_phase=0', 'cost': 702.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 702.0, 'raw_cost': 702.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '2_phase=0', 'cost': 585.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 585.0, 'raw_cost': 585.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0}],
+            [{'id': '4_phase=2', 'cost': 3656.25, 'gain': 2.0, 'type': 'suspended_floor_insulation',
+              'innovation_uplift': 0, 'cost_minus_uplift': 3656.25, 'raw_cost': 3656.25, 'partial_project_funding': 0,
+              'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False, 'has_battery': False,
+              'array_size': 0}],
+            [{'id': '5_phase=3', 'cost': 17.5, 'gain': 1.0, 'type': 'low_energy_lighting', 'innovation_uplift': 0,
+              'cost_minus_uplift': 17.5, 'raw_cost': 17.5, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '6_phase=4', 'cost': 140, 'gain': 3.4, 'type': 'roomstat_programmer_trvs', 'innovation_uplift': 0,
+              'cost_minus_uplift': 140, 'raw_cost': 140, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0},
+             {'id': '7_phase=4', 'cost': 874.5680000000001, 'gain': 4.2, 'type': 'time_temperature_zone_control',
+              'innovation_uplift': 0, 'cost_minus_uplift': 874.5680000000001, 'raw_cost': 874.5680000000001,
+              'partial_project_funding': 0, 'partial_project_score': 0, 'uplift_project_score': 0,
+              'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '9_phase=6', 'cost': 5420.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5420.0, 'raw_cost': 5420.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.6},
+             {'id': '10_phase=6', 'cost': 6210.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6210.0, 'raw_cost': 6210.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '11_phase=6', 'cost': 6820.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6820.0, 'raw_cost': 6820.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '12_phase=6', 'cost': 7202.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7202.0, 'raw_cost': 7202.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.915},
+             {'id': '13_phase=6', 'cost': 6495.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6495.0, 'raw_cost': 6495.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.92},
+             {'id': '14_phase=6', 'cost': 7285.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7285.0, 'raw_cost': 7285.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '15_phase=6', 'cost': 7895.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7895.0, 'raw_cost': 7895.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '16_phase=6', 'cost': 5520.0, 'gain': 15.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5520.0, 'raw_cost': 5520.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 4.0},
+             {'id': '17_phase=6', 'cost': 6310.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6310.0, 'raw_cost': 6310.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '18_phase=6', 'cost': 6920.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6920.0, 'raw_cost': 6920.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '19_phase=6', 'cost': 5320.0, 'gain': 12.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5320.0, 'raw_cost': 5320.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.2},
+             {'id': '20_phase=6', 'cost': 6110.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6110.0, 'raw_cost': 6110.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '21_phase=6', 'cost': 6720.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6720.0, 'raw_cost': 6720.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '22_phase=6', 'cost': 6932.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6932.0, 'raw_cost': 6932.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '23_phase=6', 'cost': 6295.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6295.0, 'raw_cost': 6295.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '24_phase=6', 'cost': 7085.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7085.0, 'raw_cost': 7085.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '25_phase=6', 'cost': 7695.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7695.0, 'raw_cost': 7695.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '26_phase=6', 'cost': 5220.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5220.0, 'raw_cost': 5220.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.8},
+             {'id': '27_phase=6', 'cost': 6662.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6662.0, 'raw_cost': 6662.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.045},
+             {'id': '28_phase=6', 'cost': 6095.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6095.0, 'raw_cost': 6095.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.05},
+             {'id': '29_phase=6', 'cost': 5160.0, 'gain': 9.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5160.0, 'raw_cost': 5160.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.4},
+             {'id': '30_phase=6', 'cost': 6392.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6392.0, 'raw_cost': 6392.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '31_phase=6', 'cost': 5910.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5910.0, 'raw_cost': 5910.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '32_phase=6', 'cost': 5100.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5100.0, 'raw_cost': 5100.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.0},
+             {'id': '33_phase=6', 'cost': 6098.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6098.0, 'raw_cost': 6098.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.175},
+             {'id': '34_phase=6', 'cost': 5725.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5725.0, 'raw_cost': 5725.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.18},
+             {'id': '35_phase=6', 'cost': 5040.0, 'gain': 6.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5040.0, 'raw_cost': 5040.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.6},
+             {'id': '36_phase=6', 'cost': 5828.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5828.0, 'raw_cost': 5828.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74},
+             {'id': '37_phase=6', 'cost': 5540.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5540.0, 'raw_cost': 5540.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74}
+             ]
+        ]
+        budget = 5000
+        target_gain = 11.5
+
+        opt = StrategicOptimiser(
+            components=components,
+            target_gain=target_gain,
+            budget=budget,
+        )
+
+        opt.solve()
+
+        # check strategy used
+        assert opt.strategy_used.value == "case_1_try_min_cost_with_constraints"
+        # Check the solution values
+        assert opt.solution_cost == 4398.75
+        assert opt.solution_gain == 12
+
+    def test_budget_and_target_gain_2(self):
+        components = [
+            [
+                {'id': '0_phase=0', 'cost': 819.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 819.0, 'raw_cost': 819.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '1_phase=0', 'cost': 702.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 702.0, 'raw_cost': 702.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '2_phase=0', 'cost': 585.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 585.0, 'raw_cost': 585.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0}],
+            [{'id': '4_phase=2', 'cost': 3656.25, 'gain': 2.0, 'type': 'suspended_floor_insulation',
+              'innovation_uplift': 0, 'cost_minus_uplift': 3656.25, 'raw_cost': 3656.25, 'partial_project_funding': 0,
+              'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False, 'has_battery': False,
+              'array_size': 0}],
+            [{'id': '5_phase=3', 'cost': 17.5, 'gain': 1.0, 'type': 'low_energy_lighting', 'innovation_uplift': 0,
+              'cost_minus_uplift': 17.5, 'raw_cost': 17.5, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '6_phase=4', 'cost': 140, 'gain': 3.4, 'type': 'roomstat_programmer_trvs', 'innovation_uplift': 0,
+              'cost_minus_uplift': 140, 'raw_cost': 140, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0},
+             {'id': '7_phase=4', 'cost': 874.5680000000001, 'gain': 4.2, 'type': 'time_temperature_zone_control',
+              'innovation_uplift': 0, 'cost_minus_uplift': 874.5680000000001, 'raw_cost': 874.5680000000001,
+              'partial_project_funding': 0, 'partial_project_score': 0, 'uplift_project_score': 0,
+              'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '9_phase=6', 'cost': 5420.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5420.0, 'raw_cost': 5420.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.6},
+             {'id': '10_phase=6', 'cost': 6210.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6210.0, 'raw_cost': 6210.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '11_phase=6', 'cost': 6820.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6820.0, 'raw_cost': 6820.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '12_phase=6', 'cost': 7202.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7202.0, 'raw_cost': 7202.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.915},
+             {'id': '13_phase=6', 'cost': 6495.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6495.0, 'raw_cost': 6495.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.92},
+             {'id': '14_phase=6', 'cost': 7285.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7285.0, 'raw_cost': 7285.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '15_phase=6', 'cost': 7895.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7895.0, 'raw_cost': 7895.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '16_phase=6', 'cost': 5520.0, 'gain': 15.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5520.0, 'raw_cost': 5520.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 4.0},
+             {'id': '17_phase=6', 'cost': 6310.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6310.0, 'raw_cost': 6310.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '18_phase=6', 'cost': 6920.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6920.0, 'raw_cost': 6920.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '19_phase=6', 'cost': 5320.0, 'gain': 12.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5320.0, 'raw_cost': 5320.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.2},
+             {'id': '20_phase=6', 'cost': 6110.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6110.0, 'raw_cost': 6110.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '21_phase=6', 'cost': 6720.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6720.0, 'raw_cost': 6720.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '22_phase=6', 'cost': 6932.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6932.0, 'raw_cost': 6932.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '23_phase=6', 'cost': 6295.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6295.0, 'raw_cost': 6295.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '24_phase=6', 'cost': 7085.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7085.0, 'raw_cost': 7085.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '25_phase=6', 'cost': 7695.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7695.0, 'raw_cost': 7695.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '26_phase=6', 'cost': 5220.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5220.0, 'raw_cost': 5220.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.8},
+             {'id': '27_phase=6', 'cost': 6662.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6662.0, 'raw_cost': 6662.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.045},
+             {'id': '28_phase=6', 'cost': 6095.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6095.0, 'raw_cost': 6095.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.05},
+             {'id': '29_phase=6', 'cost': 5160.0, 'gain': 9.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5160.0, 'raw_cost': 5160.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.4},
+             {'id': '30_phase=6', 'cost': 6392.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6392.0, 'raw_cost': 6392.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '31_phase=6', 'cost': 5910.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5910.0, 'raw_cost': 5910.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '32_phase=6', 'cost': 5100.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5100.0, 'raw_cost': 5100.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.0},
+             {'id': '33_phase=6', 'cost': 6098.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6098.0, 'raw_cost': 6098.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.175},
+             {'id': '34_phase=6', 'cost': 5725.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5725.0, 'raw_cost': 5725.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.18},
+             {'id': '35_phase=6', 'cost': 5040.0, 'gain': 6.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5040.0, 'raw_cost': 5040.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.6},
+             {'id': '36_phase=6', 'cost': 5828.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5828.0, 'raw_cost': 5828.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74},
+             {'id': '37_phase=6', 'cost': 5540.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5540.0, 'raw_cost': 5540.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74}
+             ]
+        ]
+        budget = 4000
+        target_gain = 11.5
+
+        opt = StrategicOptimiser(
+            components=components,
+            target_gain=target_gain,
+            budget=budget,
+        )
+
+        opt.solve()
+
+        # We expect to use case 1, but we won't be able to meet the target gain, so we should get the best solution
+        # possible within the budget. We end up with an infeasible solution when we try
+        # case_1_try_min_cost_with_constraints
+        assert opt.strategy_used.value == "case_1_solve_max_gain_under_budget"
+        assert opt.solution_cost == 1477.0680000000002
+        assert opt.solution_gain == 10.8
+
+    def test_just_gain(self):
+        components = [
+            [
+                {'id': '0_phase=0', 'cost': 819.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 819.0, 'raw_cost': 819.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '1_phase=0', 'cost': 702.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 702.0, 'raw_cost': 702.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '2_phase=0', 'cost': 585.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 585.0, 'raw_cost': 585.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0}],
+            [{'id': '4_phase=2', 'cost': 3656.25, 'gain': 2.0, 'type': 'suspended_floor_insulation',
+              'innovation_uplift': 0, 'cost_minus_uplift': 3656.25, 'raw_cost': 3656.25, 'partial_project_funding': 0,
+              'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False, 'has_battery': False,
+              'array_size': 0}],
+            [{'id': '5_phase=3', 'cost': 17.5, 'gain': 1.0, 'type': 'low_energy_lighting', 'innovation_uplift': 0,
+              'cost_minus_uplift': 17.5, 'raw_cost': 17.5, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '6_phase=4', 'cost': 140, 'gain': 3.4, 'type': 'roomstat_programmer_trvs', 'innovation_uplift': 0,
+              'cost_minus_uplift': 140, 'raw_cost': 140, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0},
+             {'id': '7_phase=4', 'cost': 874.5680000000001, 'gain': 4.2, 'type': 'time_temperature_zone_control',
+              'innovation_uplift': 0, 'cost_minus_uplift': 874.5680000000001, 'raw_cost': 874.5680000000001,
+              'partial_project_funding': 0, 'partial_project_score': 0, 'uplift_project_score': 0,
+              'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '9_phase=6', 'cost': 5420.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5420.0, 'raw_cost': 5420.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.6},
+             {'id': '10_phase=6', 'cost': 6210.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6210.0, 'raw_cost': 6210.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '11_phase=6', 'cost': 6820.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6820.0, 'raw_cost': 6820.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '12_phase=6', 'cost': 7202.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7202.0, 'raw_cost': 7202.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.915},
+             {'id': '13_phase=6', 'cost': 6495.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6495.0, 'raw_cost': 6495.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.92},
+             {'id': '14_phase=6', 'cost': 7285.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7285.0, 'raw_cost': 7285.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '15_phase=6', 'cost': 7895.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7895.0, 'raw_cost': 7895.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '16_phase=6', 'cost': 5520.0, 'gain': 15.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5520.0, 'raw_cost': 5520.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 4.0},
+             {'id': '17_phase=6', 'cost': 6310.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6310.0, 'raw_cost': 6310.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '18_phase=6', 'cost': 6920.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6920.0, 'raw_cost': 6920.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '19_phase=6', 'cost': 5320.0, 'gain': 12.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5320.0, 'raw_cost': 5320.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.2},
+             {'id': '20_phase=6', 'cost': 6110.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6110.0, 'raw_cost': 6110.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '21_phase=6', 'cost': 6720.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6720.0, 'raw_cost': 6720.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '22_phase=6', 'cost': 6932.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6932.0, 'raw_cost': 6932.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '23_phase=6', 'cost': 6295.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6295.0, 'raw_cost': 6295.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '24_phase=6', 'cost': 7085.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7085.0, 'raw_cost': 7085.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '25_phase=6', 'cost': 7695.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7695.0, 'raw_cost': 7695.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '26_phase=6', 'cost': 5220.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5220.0, 'raw_cost': 5220.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.8},
+             {'id': '27_phase=6', 'cost': 6662.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6662.0, 'raw_cost': 6662.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.045},
+             {'id': '28_phase=6', 'cost': 6095.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6095.0, 'raw_cost': 6095.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.05},
+             {'id': '29_phase=6', 'cost': 5160.0, 'gain': 9.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5160.0, 'raw_cost': 5160.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.4},
+             {'id': '30_phase=6', 'cost': 6392.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6392.0, 'raw_cost': 6392.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '31_phase=6', 'cost': 5910.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5910.0, 'raw_cost': 5910.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '32_phase=6', 'cost': 5100.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5100.0, 'raw_cost': 5100.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.0},
+             {'id': '33_phase=6', 'cost': 6098.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6098.0, 'raw_cost': 6098.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.175},
+             {'id': '34_phase=6', 'cost': 5725.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5725.0, 'raw_cost': 5725.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.18},
+             {'id': '35_phase=6', 'cost': 5040.0, 'gain': 6.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5040.0, 'raw_cost': 5040.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.6},
+             {'id': '36_phase=6', 'cost': 5828.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5828.0, 'raw_cost': 5828.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74},
+             {'id': '37_phase=6', 'cost': 5540.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5540.0, 'raw_cost': 5540.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74}
+             ]
+        ]
+        budget = None
+        target_gain = 11.5
+
+        opt = StrategicOptimiser(
+            components=components,
+            target_gain=target_gain,
+            budget=budget,
+        )
+
+        opt.solve()
+
+        # Should be case 3 - minimise cost for target gain
+        assert opt.strategy_used.value == "case_3_solve_min_cost_for_target"
+        assert opt.solution_cost == 4398.75
+        assert opt.solution_gain == 12
+
+    def test_just_gain2(self):
+        components = [
+            [
+                {'id': '0_phase=0', 'cost': 819.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 819.0, 'raw_cost': 819.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '1_phase=0', 'cost': 702.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 702.0, 'raw_cost': 702.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '2_phase=0', 'cost': 585.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 585.0, 'raw_cost': 585.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0}],
+            [{'id': '4_phase=2', 'cost': 3656.25, 'gain': 2.0, 'type': 'suspended_floor_insulation',
+              'innovation_uplift': 0, 'cost_minus_uplift': 3656.25, 'raw_cost': 3656.25, 'partial_project_funding': 0,
+              'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False, 'has_battery': False,
+              'array_size': 0}],
+            [{'id': '5_phase=3', 'cost': 17.5, 'gain': 1.0, 'type': 'low_energy_lighting', 'innovation_uplift': 0,
+              'cost_minus_uplift': 17.5, 'raw_cost': 17.5, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '6_phase=4', 'cost': 140, 'gain': 3.4, 'type': 'roomstat_programmer_trvs', 'innovation_uplift': 0,
+              'cost_minus_uplift': 140, 'raw_cost': 140, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0},
+             {'id': '7_phase=4', 'cost': 874.5680000000001, 'gain': 4.2, 'type': 'time_temperature_zone_control',
+              'innovation_uplift': 0, 'cost_minus_uplift': 874.5680000000001, 'raw_cost': 874.5680000000001,
+              'partial_project_funding': 0, 'partial_project_score': 0, 'uplift_project_score': 0,
+              'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '9_phase=6', 'cost': 5420.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5420.0, 'raw_cost': 5420.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.6},
+             {'id': '10_phase=6', 'cost': 6210.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6210.0, 'raw_cost': 6210.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '11_phase=6', 'cost': 6820.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6820.0, 'raw_cost': 6820.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '12_phase=6', 'cost': 7202.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7202.0, 'raw_cost': 7202.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.915},
+             {'id': '13_phase=6', 'cost': 6495.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6495.0, 'raw_cost': 6495.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.92},
+             {'id': '14_phase=6', 'cost': 7285.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7285.0, 'raw_cost': 7285.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '15_phase=6', 'cost': 7895.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7895.0, 'raw_cost': 7895.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '16_phase=6', 'cost': 5520.0, 'gain': 15.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5520.0, 'raw_cost': 5520.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 4.0},
+             {'id': '17_phase=6', 'cost': 6310.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6310.0, 'raw_cost': 6310.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '18_phase=6', 'cost': 6920.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6920.0, 'raw_cost': 6920.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '19_phase=6', 'cost': 5320.0, 'gain': 12.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5320.0, 'raw_cost': 5320.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.2},
+             {'id': '20_phase=6', 'cost': 6110.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6110.0, 'raw_cost': 6110.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '21_phase=6', 'cost': 6720.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6720.0, 'raw_cost': 6720.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '22_phase=6', 'cost': 6932.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6932.0, 'raw_cost': 6932.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '23_phase=6', 'cost': 6295.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6295.0, 'raw_cost': 6295.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '24_phase=6', 'cost': 7085.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7085.0, 'raw_cost': 7085.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '25_phase=6', 'cost': 7695.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7695.0, 'raw_cost': 7695.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '26_phase=6', 'cost': 5220.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5220.0, 'raw_cost': 5220.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.8},
+             {'id': '27_phase=6', 'cost': 6662.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6662.0, 'raw_cost': 6662.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.045},
+             {'id': '28_phase=6', 'cost': 6095.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6095.0, 'raw_cost': 6095.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.05},
+             {'id': '29_phase=6', 'cost': 5160.0, 'gain': 9.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5160.0, 'raw_cost': 5160.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.4},
+             {'id': '30_phase=6', 'cost': 6392.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6392.0, 'raw_cost': 6392.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '31_phase=6', 'cost': 5910.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5910.0, 'raw_cost': 5910.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '32_phase=6', 'cost': 5100.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5100.0, 'raw_cost': 5100.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.0},
+             {'id': '33_phase=6', 'cost': 6098.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6098.0, 'raw_cost': 6098.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.175},
+             {'id': '34_phase=6', 'cost': 5725.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5725.0, 'raw_cost': 5725.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.18},
+             {'id': '35_phase=6', 'cost': 5040.0, 'gain': 6.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5040.0, 'raw_cost': 5040.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.6},
+             {'id': '36_phase=6', 'cost': 5828.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5828.0, 'raw_cost': 5828.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74},
+             {'id': '37_phase=6', 'cost': 5540.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5540.0, 'raw_cost': 5540.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74}
+             ]
+        ]
+        budget = None
+        target_gain = 20
+
+        opt = StrategicOptimiser(
+            components=components,
+            target_gain=target_gain,
+            budget=budget,
+        )
+
+        opt.solve()
+
+        # Should be case 3 - minimise cost for target gain
+        assert opt.strategy_used.value == "case_3_solve_min_cost_for_target"
+        assert opt.solution_cost == 5962.5
+        assert opt.solution_gain == 20.2
+
+    def test_just_budget(self):
+        components = [
+            [
+                {'id': '0_phase=0', 'cost': 819.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 819.0, 'raw_cost': 819.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '1_phase=0', 'cost': 702.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 702.0, 'raw_cost': 702.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0},
+                {'id': '2_phase=0', 'cost': 585.0, 'gain': 5.6, 'type': 'loft_insulation', 'innovation_uplift': 0,
+                 'cost_minus_uplift': 585.0, 'raw_cost': 585.0, 'partial_project_funding': 0,
+                 'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False,
+                 'has_battery': False, 'array_size': 0}],
+            [{'id': '4_phase=2', 'cost': 3656.25, 'gain': 2.0, 'type': 'suspended_floor_insulation',
+              'innovation_uplift': 0, 'cost_minus_uplift': 3656.25, 'raw_cost': 3656.25, 'partial_project_funding': 0,
+              'partial_project_score': 0, 'uplift_project_score': 0, 'already_installed': False, 'has_battery': False,
+              'array_size': 0}],
+            [{'id': '5_phase=3', 'cost': 17.5, 'gain': 1.0, 'type': 'low_energy_lighting', 'innovation_uplift': 0,
+              'cost_minus_uplift': 17.5, 'raw_cost': 17.5, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '6_phase=4', 'cost': 140, 'gain': 3.4, 'type': 'roomstat_programmer_trvs', 'innovation_uplift': 0,
+              'cost_minus_uplift': 140, 'raw_cost': 140, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 0},
+             {'id': '7_phase=4', 'cost': 874.5680000000001, 'gain': 4.2, 'type': 'time_temperature_zone_control',
+              'innovation_uplift': 0, 'cost_minus_uplift': 874.5680000000001, 'raw_cost': 874.5680000000001,
+              'partial_project_funding': 0, 'partial_project_score': 0, 'uplift_project_score': 0,
+              'already_installed': False, 'has_battery': False, 'array_size': 0}],
+            [{'id': '9_phase=6', 'cost': 5420.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5420.0, 'raw_cost': 5420.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.6},
+             {'id': '10_phase=6', 'cost': 6210.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6210.0, 'raw_cost': 6210.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '11_phase=6', 'cost': 6820.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6820.0, 'raw_cost': 6820.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.6,
+              'battery_gain': 3},
+             {'id': '12_phase=6', 'cost': 7202.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7202.0, 'raw_cost': 7202.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.915},
+             {'id': '13_phase=6', 'cost': 6495.0, 'gain': 14.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6495.0, 'raw_cost': 6495.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.92},
+             {'id': '14_phase=6', 'cost': 7285.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7285.0, 'raw_cost': 7285.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '15_phase=6', 'cost': 7895.0, 'gain': 17.5, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7895.0, 'raw_cost': 7895.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.92,
+              'battery_gain': 3},
+             {'id': '16_phase=6', 'cost': 5520.0, 'gain': 15.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5520.0, 'raw_cost': 5520.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 4.0},
+             {'id': '17_phase=6', 'cost': 6310.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6310.0, 'raw_cost': 6310.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '18_phase=6', 'cost': 6920.0, 'gain': 18.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6920.0, 'raw_cost': 6920.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 4.0,
+              'battery_gain': 3},
+             {'id': '19_phase=6', 'cost': 5320.0, 'gain': 12.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5320.0, 'raw_cost': 5320.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.2},
+             {'id': '20_phase=6', 'cost': 6110.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6110.0, 'raw_cost': 6110.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '21_phase=6', 'cost': 6720.0, 'gain': 14.1, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6720.0, 'raw_cost': 6720.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.2,
+              'battery_gain': 2},
+             {'id': '22_phase=6', 'cost': 6932.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6932.0, 'raw_cost': 6932.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '23_phase=6', 'cost': 6295.0, 'gain': 13.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6295.0, 'raw_cost': 6295.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.48},
+             {'id': '24_phase=6', 'cost': 7085.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7085.0, 'raw_cost': 7085.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '25_phase=6', 'cost': 7695.0, 'gain': 16.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 7695.0, 'raw_cost': 7695.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': True, 'array_size': 3.48,
+              'battery_gain': 3},
+             {'id': '26_phase=6', 'cost': 5220.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5220.0, 'raw_cost': 5220.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.8},
+             {'id': '27_phase=6', 'cost': 6662.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6662.0, 'raw_cost': 6662.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.045},
+             {'id': '28_phase=6', 'cost': 6095.0, 'gain': 12.3, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6095.0, 'raw_cost': 6095.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 3.05},
+             {'id': '29_phase=6', 'cost': 5160.0, 'gain': 9.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5160.0, 'raw_cost': 5160.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.4},
+             {'id': '30_phase=6', 'cost': 6392.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6392.0, 'raw_cost': 6392.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '31_phase=6', 'cost': 5910.0, 'gain': 10.2, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5910.0, 'raw_cost': 5910.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.61},
+             {'id': '32_phase=6', 'cost': 5100.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5100.0, 'raw_cost': 5100.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.0},
+             {'id': '33_phase=6', 'cost': 6098.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 6098.0, 'raw_cost': 6098.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.175},
+             {'id': '34_phase=6', 'cost': 5725.0, 'gain': 8.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5725.0, 'raw_cost': 5725.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 2.18},
+             {'id': '35_phase=6', 'cost': 5040.0, 'gain': 6.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5040.0, 'raw_cost': 5040.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.6},
+             {'id': '36_phase=6', 'cost': 5828.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5828.0, 'raw_cost': 5828.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74},
+             {'id': '37_phase=6', 'cost': 5540.0, 'gain': 7.0, 'type': 'solar_pv', 'innovation_uplift': 0,
+              'cost_minus_uplift': 5540.0, 'raw_cost': 5540.0, 'partial_project_funding': 0, 'partial_project_score': 0,
+              'uplift_project_score': 0, 'already_installed': False, 'has_battery': False, 'array_size': 1.74}
+             ]
+        ]
+        budget = 10000
+        target_gain = None
+
+        opt = StrategicOptimiser(
+            components=components,
+            target_gain=target_gain,
+            budget=budget,
+        )
+
+        opt.solve()
+
+        # Should be case 3 - minimise cost for target gain
+        assert opt.strategy_used.value == "case_2_solve_max_gain_under_budget"
+        assert opt.solution_cost == 7787.068
+        assert opt.solution_gain == 28.8