PyTest ExampleMemoized function embedded in a handler function

test_things.py

from unittest import mock

import thing

import pytest


@pytest.fixture()
def mock_client(monkeypatch, request):
    """Mock the client."""
    mock_client = mock.create_autospec(thing.client)

    monkeypatch.setattr(thing, "client", mock_client)

    def _teardown():
        thing.exists.cache_clear()

    request.addfinalizer(_teardown)

    return mock_client


@pytest.mark.parametrize(
    "does_use_cache, does_key_exist",
    [(True, True), (True, False), (False, True), (False, False)]
)
def test_key_exists(mock_client, does_use_cache, does_key_exist):
    if not does_key_exist:
        mock_client.head_object.side_effect = thing.Client.ClientException

    count = 2
    bucket = thing.s3_bucket
    key = "key"
    call_args_list = list()

    for i in range(count):
        exists = thing.exists(key)

        assert exists if does_key_exist else not exists

        if i == 0 or not does_use_cache:
            call_args_list.append(mock.call(Bucket=bucket, Key=key))

        if not does_use_cache:
            thing.exists.cache_clear()

    assert mock_client.head_object.call_count == 1 if does_use_cache else count
    assert mock_client.head_object.call_args_list == call_args_list


@pytest.mark.parametrize("status_code", [(200), (404)])
def test_the_handler(mock_client, status_code):
    """Test the handler."""
    if status_code == 404:
        mock_client.head_object.side_effect = thing.Client.ClientException

    key = "key"
    response = thing.handler(key)

    assert response["statusCode"] == status_code

thing.py

"""Example python source."""
import functools
import json
import os


class Client:
    """This is a client."""
    class ClientException(Exception):
        pass

    def head_object(self, Bucket=None, Key=None):
        """This is a dummy head_object.

        No. You are a dummy head."""
        pass


@functools.lru_cache(maxsize=2)
def exists(key):
    """Return True."""
    try:
        client.head_object(Bucket=s3_bucket, Key=key)
    except Client.ClientException:
        return False

    return True


def handler(key, times=1):
    """The handler."""
    for _ in range(times):
        if not exists(key):
            return {
                "statusCode": 404,
                "body": json.dumps({"body": "Not Found"})
            }

    return {
        "statusCode": 200,
        "body": json.dumps({"body": "Found"})
    }


client = Client()
s3_bucket = os.getenv("BUCKET", "bucket")