Validate that campaign config end date is not before start date.

Author: acerathereinspirative-nhs-nvir

src/eligibility_signposting_api/model/rules.py

@@ -163,6 +163,13 @@ def parse_dates(cls, v: str | date) -> date:
     def serialize_dates(v: date, _info: SerializationInfo) -> str:
         return v.strftime("%Y%m%d")
 
+    @model_validator(mode="after")
+    def check_start_and_end_dates_sensible(self) -> typing.Self:
+        if self.start_date > self.end_date:
+            message = f"start date {self.start_date} after end date {self.end_date}"
+            raise ValueError(message)
+        return self
+
     @model_validator(mode="after")
     def check_no_overlapping_iterations(self) -> typing.Self:
         iterations_by_date = Counter([i.iteration_date for i in self.iterations])

tests/unit/model/test_rules.py

@@ -5,6 +5,20 @@
 from tests.fixtures.builders.model.rule import IterationFactory, RawCampaignConfigFactory
 
 
+def test_start_date_must_be_before_end_date(faker: Faker):
+    # Given
+    start_date = faker.date_object()
+    end_date = start_date - relativedelta(days=1)
+
+    # When, Then
+    with pytest.raises(
+        ValueError,
+        match=r"1 validation error for CampaignConfig\n"
+        r".*start date .* after end date",
+    ):
+        RawCampaignConfigFactory.build(start_date=start_date, end_date=end_date)
+
+
 def test_iteration_with_overlapping_start_dates_not_allowed(faker: Faker):
     # Given
     start_date = faker.date_object()