test(podcasts): cover structured json parsing

surfsense_backend/tests/unit/podcasts/test_structured.py

@@ -0,0 +1,68 @@
+"""Parsing a model's reply into a structured shape.
+
+Agent LLMs wrap JSON in prose and markdown fences. ``invoke_json`` exists so
+every generation node tolerates that the same way. The LLM is an external
+boundary, so it is faked with a canned reply; the behavior under test is the
+parsing, not the model.
+"""
+
+from __future__ import annotations
+
+import pytest
+from pydantic import BaseModel
+
+from app.podcasts.generation.structured import StructuredOutputError, invoke_json
+
+pytestmark = pytest.mark.unit
+
+
+class _Shape(BaseModel):
+    name: str
+    count: int
+
+
+class _CannedLLM:
+    """A TTS-free stand-in for the chat model: replies with one fixed string."""
+
+    def __init__(self, reply: str) -> None:
+        self._reply = reply
+
+    async def ainvoke(self, _messages):
+        return SimpleReply(self._reply)
+
+
+class SimpleReply:
+    def __init__(self, content: str) -> None:
+        self.content = content
+
+
+async def _parse(reply: str) -> _Shape:
+    return await invoke_json(_CannedLLM(reply), [], _Shape)
+
+
+async def test_parses_a_clean_json_reply():
+    shape = await _parse('{"name": "alpha", "count": 3}')
+    assert shape == _Shape(name="alpha", count=3)
+
+
+async def test_parses_json_wrapped_in_a_markdown_fence():
+    reply = '```json\n{"name": "beta", "count": 7}\n```'
+    shape = await _parse(reply)
+    assert shape == _Shape(name="beta", count=7)
+
+
+async def test_extracts_json_embedded_in_prose():
+    """Reasoning models prepend/append chatter around the object."""
+    reply = 'Sure, here you go: {"name": "gamma", "count": 1} — hope that helps!'
+    shape = await _parse(reply)
+    assert shape == _Shape(name="gamma", count=1)
+
+
+async def test_raises_when_there_is_no_json_object():
+    with pytest.raises(StructuredOutputError):
+        await _parse("I could not produce that.")
+
+
+async def test_raises_when_the_json_does_not_match_the_shape():
+    with pytest.raises(StructuredOutputError):
+        await _parse('{"name": "delta"}')