fix(tests): Fix test case for Prometheus metrics

Disable prometheus multiprocess mode in tests to avoid global state:
Depending on the workers which are processing a testfile,
we might run into race issues where tests might influence each other.

We also need to make sure to clear any previously collected values
in case the same worker/process is executing different tests which
evaluate prometheus values.

Signed-off-by: moson <moson@archlinux.org>

test/test_statistics.py

@@ -1,7 +1,7 @@
 import pytest
 from prometheus_client import REGISTRY, generate_latest
 
-from aurweb import cache, db, prometheus, time
+from aurweb import cache, db, time
 from aurweb.models import Package, PackageBase, PackageRequest
 from aurweb.models.account_type import PACKAGE_MAINTAINER_ID, USER_ID
 from aurweb.models.package_request import (
@@ -16,7 +16,7 @@ from aurweb.statistics import Statistics, update_prometheus_metrics
 
 
 @pytest.fixture(autouse=True)
-def setup(db_test):
+def setup(db_test, prometheus_test):
     return
 
 
@@ -140,11 +140,6 @@ def test_get_count_change(stats: Statistics, test_data):
 
 
 def test_update_prometheus_metrics(test_data):
-    # Make sure any previous data is cleared
-    prometheus.USERS.clear()
-    prometheus.PACKAGES.clear()
-    prometheus.REQUESTS.clear()
-
     metrics = str(generate_latest(REGISTRY))
 
     assert "aur_users{" not in metrics