"""Tests for Prometheus metrics exposed by the OCR service.

Each test that asserts on a counter/gauge value uses a fresh CollectorRegistry
(see decision #3 on issue #652) to keep the metrics isolated between tests.
"""

from unittest.mock import patch

import pytest
from httpx import ASGITransport, AsyncClient

from main import app


@pytest.mark.asyncio
async def test_metrics_endpoint_returns_200():
    """`GET /metrics` returns 200 with Prometheus exposition content."""
    with patch("main.kraken_engine.load_models"), \
         patch("main.load_spell_checker"):
        async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as client:
            response = await client.get("/metrics")

    assert response.status_code == 200
    assert "text/plain" in response.headers.get("content-type", "")