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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"unittest.mock: Regression with create_autospec and dataclasses in 3.14.0b2","articleBody":"# Bug report\n\n### Bug description:\n\n```python\nfrom dataclasses import dataclass\nfrom unittest.mock import create_autospec\n\n@dataclass\nclass Description:\n    name: str\n\nmock = create_autospec(Description, instance=True)\nprint(isinstance(mock, Description))\n```\n```py\n# 3.13.3\nTrue\n\n# 3.14.0b2\nFalse\n```\n\nFurthermore the resulting mock doesn't have attributes present on a dataclass instance, like `__annotations__`, `__class__`, `__dataclass_fields__`, `__dataclass_params__`. \n```py\nprint(dir(mock))\nprint(dir(Description(\"Hello World\"))\n```\n\nLikely related to #124429. /CC @sobolevn\n\n### CPython versions tested on:\n\n3.14\n\n### Operating systems tested on:\n\nmacOS\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-135421\n* gh-135503\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/cdce8p","@type":"Person","name":"cdce8p"},"datePublished":"2025-06-10T22:21:12.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/135368/cpython/issues/135368"}