Model/tests/infrastructure/test_http_retry.py

"""call_with_retry — the shared transient-failure retry both HTTP source clients
use. Generic mechanism (exponential backoff, Retry-After), per-client policy
(what gets raised as transient)."""

from __future__ import annotations

from typing import Iterator
from unittest.mock import MagicMock, call, patch

import httpx
import pytest

from infrastructure.http_retry import TransientHttpError, call_with_retry


@pytest.fixture(autouse=True)
def _no_sleep() -> Iterator[MagicMock]:
    with patch("infrastructure.http_retry.time.sleep") as sleep:
        yield sleep


def test_returns_immediately_on_success(_no_sleep: MagicMock) -> None:
    # Act
    result = call_with_retry(lambda: 42)

    # Assert
    assert result == 42
    _no_sleep.assert_not_called()


def test_retries_a_transient_error_then_succeeds(_no_sleep: MagicMock) -> None:
    # Arrange — fail twice transiently, then succeed.
    calls = {"n": 0}

    def fn() -> str:
        calls["n"] += 1
        if calls["n"] < 3:
            raise TransientHttpError("429")
        return "ok"

    # Act
    result = call_with_retry(fn)

    # Assert — exponential backoff between the three attempts.
    assert result == "ok"
    assert _no_sleep.call_args_list == [call(1.0), call(2.0)]


def test_honours_retry_after_over_the_computed_backoff(_no_sleep: MagicMock) -> None:
    # Arrange
    raised = {"done": False}

    def fn() -> str:
        if not raised["done"]:
            raised["done"] = True
            raise TransientHttpError("429", retry_after=7.0)
        return "ok"

    # Act
    call_with_retry(fn)

    # Assert
    _no_sleep.assert_called_once_with(7.0)


def test_retries_transport_errors(_no_sleep: MagicMock) -> None:
    # Arrange
    attempts = {"n": 0}

    def fn() -> str:
        attempts["n"] += 1
        if attempts["n"] == 1:
            raise httpx.ReadTimeout("slow")
        return "ok"

    # Act
    result = call_with_retry(fn)

    # Assert
    assert result == "ok"
    assert attempts["n"] == 2


def test_reraises_the_last_transient_error_once_exhausted(
    _no_sleep: MagicMock,
) -> None:
    # Arrange — always transient.
    def fn() -> str:
        raise TransientHttpError("persistent 429")

    # Act / Assert
    with pytest.raises(TransientHttpError, match="persistent 429"):
        call_with_retry(fn, max_retries=2)
    assert _no_sleep.call_count == 2


def test_non_transient_error_propagates_without_retry(_no_sleep: MagicMock) -> None:
    # Arrange
    attempts = {"n": 0}

    def fn() -> str:
        attempts["n"] += 1
        raise ValueError("not transient")

    # Act / Assert
    with pytest.raises(ValueError, match="not transient"):
        call_with_retry(fn)
    assert attempts["n"] == 1
    _no_sleep.assert_not_called()


def test_jitter_full_randomizes_the_computed_backoff(_no_sleep: MagicMock) -> None:
    # Arrange — fail once transiently (no server Retry-After), then succeed.
    calls = {"n": 0}

    def fn() -> str:
        calls["n"] += 1
        if calls["n"] < 2:
            raise TransientHttpError("429")
        return "ok"

    # Act — full jitter draws the sleep uniformly from [0, computed_backoff].
    with patch("infrastructure.http_retry.random.uniform", return_value=0.4) as runi:
        result = call_with_retry(fn, jitter=True)

    # Assert — the first computed backoff is 1.0; jitter draws over [0, 1.0]
    # and the drawn value is what we sleep for (de-syncs concurrent retries).
    assert result == "ok"
    runi.assert_called_once_with(0.0, 1.0)
    _no_sleep.assert_called_once_with(0.4)


def test_jitter_does_not_apply_to_a_server_retry_after(_no_sleep: MagicMock) -> None:
    # Arrange — the server advised an exact Retry-After; jitter must not perturb it.
    raised = {"done": False}

    def fn() -> str:
        if not raised["done"]:
            raised["done"] = True
            raise TransientHttpError("429", retry_after=7.0)
        return "ok"

    # Act
    with patch("infrastructure.http_retry.random.uniform") as runi:
        call_with_retry(fn, jitter=True)

    # Assert — Retry-After is honoured verbatim, no random draw.
    runi.assert_not_called()
    _no_sleep.assert_called_once_with(7.0)


def test_retry_after_is_capped_by_max_backoff(_no_sleep: MagicMock) -> None:
    # Arrange
    raised = {"done": False}

    def fn() -> str:
        if not raised["done"]:
            raised["done"] = True
            raise TransientHttpError("429", retry_after=999.0)
        return "ok"

    # Act
    call_with_retry(fn, max_backoff=60.0)

    # Assert
    _no_sleep.assert_called_once_with(60.0)