Refs #30446 -- Added tests for resolving output_field of CombinedExpression.

tests/expressions/tests.py

@@ -15,7 +15,9 @@ from django.db.models import (
     Min, Model, OrderBy, OuterRef, Q, StdDev, Subquery, Sum, TimeField,
     UUIDField, Value, Variance, When,
 )
-from django.db.models.expressions import Col, Combinable, Random, RawSQL, Ref
+from django.db.models.expressions import (
+    Col, Combinable, CombinedExpression, Random, RawSQL, Ref,
+)
 from django.db.models.functions import (
     Coalesce, Concat, Left, Length, Lower, Substr, Upper,
 )
@@ -1888,6 +1890,26 @@ class CombinableTests(SimpleTestCase):
             object() | Combinable()
 
 
+class CombinedExpressionTests(SimpleTestCase):
+    def test_resolve_output_field(self):
+        tests = [
+            (IntegerField, DecimalField, DecimalField),
+            (DecimalField, IntegerField, DecimalField),
+            (IntegerField, FloatField, FloatField),
+            (FloatField, IntegerField, FloatField),
+        ]
+        connectors = [Combinable.ADD, Combinable.SUB, Combinable.MUL, Combinable.DIV]
+        for lhs, rhs, combined in tests:
+            for connector in connectors:
+                with self.subTest(lhs=lhs, connector=connector, rhs=rhs, combined=combined):
+                    expr = CombinedExpression(
+                        Expression(lhs()),
+                        connector,
+                        Expression(rhs()),
+                    )
+                    self.assertIsInstance(expr.output_field, combined)
+
+
 class ExpressionWrapperTests(SimpleTestCase):
     def test_empty_group_by(self):
         expr = ExpressionWrapper(Value(3), output_field=IntegerField())