Check annotations

simple_value_object/value_object.py

@@ -13,6 +13,7 @@ def __init_subclass__(cls):
         cls = dataclass(cls)
 
     def __post_init__(self):
+        self.__check_annotations()
         self.__replace_mutable_fields_with_immutable()
         self.__check_invariants()
 
@@ -39,6 +40,15 @@ def __get_mutable_fields(self):
             self.__dataclass_fields__.values(),
         )
 
+    def __check_annotations(self):
+        for field in self.__dataclass_fields__.values():
+            if not isinstance(
+                getattr(self, field.name), self.__annotations__[field.name]
+            ):
+                raise TypeError(
+                    f"{field.name} must be of type {self.__annotations__[field.name]}"
+                )
+
     def __check_invariants(self):
         for invariant in self.__obtain_invariants():
             if self.__is_invariant_violated(invariant):

specs/value_object_spec.py

@@ -252,3 +252,22 @@ def first_year_quarter(self):
                     return 0
 
             expect(lambda: Date(8, 6, 2002)).to(raise_error(InvariantMustReturnBool))
+
+    with context("ensures that defined data types are respected"):
+
+        with it("raises an exception when a field is not the expected type"):
+            expect(lambda: Point("5", 3)).to(
+                raise_error(TypeError, "x must be of type <class 'int'>")
+            )
+            expect(lambda: Point(5, "3")).to(
+                raise_error(TypeError, "y must be of type <class 'int'>")
+            )
+        with it(
+            "raises an exception when a inner value object is not the expected type"
+        ):
+            expect(lambda: Money(Decimal("100"), "€")).to(
+                raise_error(
+                    TypeError,
+                    "currency must be of type <class 'specs/value_object_spec.Currency'>",
+                )
+            )