Add default_calculation_period to test runner simulation

changelog_entry.yaml

@@ -0,0 +1,5 @@
+- bump: patch
+  changes:
+    changed:
+    - Set test runner's default period as underlying simulation's default period
+    - Prevented crashing when absolutely no date is provided anywhere for tests

policyengine_core/simulations/simulation_builder.py

@@ -28,6 +28,7 @@
     )
 
 from policyengine_core.variables import Variable
+from datetime import datetime
 
 
 class SimulationBuilder:
@@ -507,6 +508,10 @@ def add_group_entity(
     def set_default_period(self, period_str: str) -> None:
         if period_str:
             self.default_period = str(periods.period(period_str))
+        else:
+            # If at absolute worst, no period is specified anywhere,
+            # use current year
+            self.default_period = periods.period(datetime.now().year)
 
     def get_input(self, variable: str, period_str: str) -> Any:
         if variable not in self.input_buffer:

policyengine_core/tools/test_runner.py

@@ -241,6 +241,7 @@ def apply(self):
             self.simulation = builder.build_from_dict(
                 self.tax_benefit_system, input
             )
+            self.simulation.default_calculation_period = builder.default_period
         except (VariableNotFoundError, SituationParsingError):
             raise
         except Exception as e: