Add regression test

Author: danielhollas

Lib/test/test_dataclasses/__init__.py

@@ -27,11 +27,21 @@
 import dataclasses  # Needed for the string "dataclasses.InitVar[int]" to work as an annotation.
 
 from test import support
-from test.support import import_helper
+from test.support import cpython_only, import_helper
 
 # Just any custom exception we can catch.
 class CustomError(Exception): pass
 
+
+class TestImportTime(unittest.TestCase):
+
+    @cpython_only
+    def test_lazy_import(self):
+        import_helper.ensure_lazy_imports(
+            "dataclasses", {"inspect"}
+        )
+
+
 class TestCase(unittest.TestCase):
     def test_no_fields(self):
         @dataclass