Add (currently failing) tests for lovasoa#77

See python/mypy#4300

Author: lovasoa

tests/test_schema_type.py

@@ -0,0 +1,30 @@
+import unittest
+
+import marshmallow
+
+import marshmallow_dataclass
+
+
+class MyBaseSchema(marshmallow.Schema):
+    pass
+
+
+class A:
+    a: int
+
+
+# Top-level so that this is checked by mypy
+schema_with_base: MyBaseSchema = marshmallow_dataclass.class_schema(
+    A, base_schema=MyBaseSchema
+)()
+
+schema_without_base: marshmallow.Schema = marshmallow_dataclass.class_schema(A)()
+
+
+# Regression test for https://github.com/lovasoa/marshmallow_dataclass/pull/77
+class TestSchemaType(unittest.TestCase):
+    def test_custom_basechema_type(self):
+        self.assertIsInstance(schema_with_base, MyBaseSchema)
+
+    def test_no_basechema_type(self):
+        self.assertIsInstance(schema_without_base, marshmallow.Schema)