diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index ed9e8b0..4c1fd1f 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,8 +14,8 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
-        mongodb-version: ['4.2', '4.4', '5.0', '6.0']
+        python-version: ['3.10', '3.11', '3.12', '3.13']
+        mongodb-version: ['5.0', '6.0', '7.0', '8.0']
         dservercore-version: [ main ]
         dserver-search-plugin-mongo-version: [ main ]
 
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 8931b40..f5a0ee3 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -4,6 +4,23 @@ CHANGELOG
 This project uses `semantic versioning <http://semver.org/>`_.
 This change log uses principles from `keep a changelog <http://keepachangelog.com/>`_.
 
+[Unreleased]
+------------
+
+Changed
+^^^^^^^
+
+- Dropped support for Python 3.7–3.9; minimum is now Python 3.10
+- Updated CI Python matrix to 3.10–3.13; updated MongoDB matrix to 5.0–8.0
+
+Fixed
+^^^^^
+
+- Test fixtures: hardcoded MongoDB URI replaced by ``MONGO_URI`` environment variable (default: ``mongodb://localhost:27017/``)
+- Test fixtures: added ``client.close()`` after ``drop_database()`` in teardown to prevent connection pool exhaustion
+- Test fixtures: removed stale ``FLASK_ENV`` key from app config (removed in Flask 3.0)
+- Config route test: URI assertion now reads from ``MONGO_URI`` environment variable
+
 [0.4.2]
 -------
 
diff --git a/pyproject.toml b/pyproject.toml
index 5829c47..bfd480e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -12,6 +12,7 @@ authors = [
     {name = "Johannes L. Hörmann", email = "johannes.laurin@gmail.com"},
 ]
 dynamic = ["version"]
+requires-python = ">=3.10"
 dependencies = [
         "pymongo",
         "dtoolcore>=3.18.0",
diff --git a/tests/conftest.py b/tests/conftest.py
index a436a43..3f8b24c 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,5 +1,6 @@
 """Reusable fixtures"""
 
+import os
 import random
 import string
 
@@ -7,6 +8,7 @@
 
 JWT_PUBLIC_KEY = "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC8LrEp0Q6l1WPsY32uOPqEjaisQScnzO/XvlhQTzj5w+hFObjiNgIaHRceYh3hZZwsRsHIkCxOY0JgUPeFP9IVXso0VptIjCPRF5yrV/+dF1rtl4eyYj/XOBvSDzbQQwqdjhHffw0TXW0f/yjGGJCYM+tw/9dmj9VilAMNTx1H76uPKUo4M3vLBQLo2tj7z1jlh4Jlw5hKBRcWQWbpWP95p71Db6gSpqReDYbx57BW19APMVketUYsXfXTztM/HWz35J9HDya3ID0Dl+pE22Wo8SZo2+ULKu/4OYVcD8DjF15WwXrcuFDypX132j+LUWOVWxCs5hdMybSDwF3ZhVBH ec2-user@ip-172-31-41-191.eu-west-1.compute.internal"  # NOQA
 
+MONGO_URI = os.environ.get("MONGO_URI", "mongodb://localhost:27017/")
 
 
 def random_string(
@@ -41,12 +43,11 @@ def tmp_app_with_users(request):
         "OPENAPI_VERSION": '3.0.2',
         "CONFIG_SECRETS_TO_OBFUSCATE": [],
         "SECRET_KEY": "secret",
-        "FLASK_ENV": "development",
         "SQLALCHEMY_DATABASE_URI": "sqlite:///:memory:",
-        "RETRIEVE_MONGO_URI": "mongodb://localhost:27017/",
+        "RETRIEVE_MONGO_URI": MONGO_URI,
         "RETRIEVE_MONGO_DB": tmp_mongo_db_name,
         "RETRIEVE_MONGO_COLLECTION": "datasets",
-        "SEARCH_MONGO_URI": "mongodb://localhost:27017/",
+        "SEARCH_MONGO_URI": MONGO_URI,
         "SEARCH_MONGO_DB": tmp_mongo_db_name,
         "SEARCH_MONGO_COLLECTION": "datasets",
         "SQLALCHEMY_TRACK_MODIFICATIONS": False,
@@ -84,7 +85,9 @@ def tmp_app_with_users(request):
     @request.addfinalizer
     def teardown():
         current_app.retrieve.client.drop_database(tmp_mongo_db_name)
+        current_app.retrieve.client.close()
         current_app.search.client.drop_database(tmp_mongo_db_name)
+        current_app.search.client.close()
         sql_db.session.remove()
 
-    return app.test_client()
\ No newline at end of file
+    return app.test_client()
diff --git a/tests/test_config_route.py b/tests/test_config_route.py
index e81125a..7db0ec8 100644
--- a/tests/test_config_route.py
+++ b/tests/test_config_route.py
@@ -1,6 +1,7 @@
 """Test the /config blueprint route."""
 
 import json
+import os
 import dserver_retrieve_plugin_mongo
 
 from .utils import compare_nested
@@ -17,7 +18,7 @@ def test_config_info_route(tmp_app_with_users, snowwhite_token):  # NOQA
 
     expected_content = {
           'retrieve_mongo_collection': 'datasets',
-          'retrieve_mongo_uri': 'mongodb://localhost:27017/',
+          'retrieve_mongo_uri': os.environ.get("MONGO_URI", "mongodb://localhost:27017/"),
     }
 
     response = json.loads(r.data.decode("utf-8"))
diff --git a/tests/test_utils_retrieve_standalone.py b/tests/test_utils_retrieve_standalone.py
index 410fa34..d96d2b7 100644
--- a/tests/test_utils_retrieve_standalone.py
+++ b/tests/test_utils_retrieve_standalone.py
@@ -20,8 +20,8 @@
 # This tested in this module.
 from dserver_retrieve_plugin_mongo.utils_retrieve import MongoRetrieve
 
-
-MONGO_URI = "mongodb://localhost:27017"
+import os
+MONGO_URI = os.environ.get("MONGO_URI", "mongodb://localhost:27017/")
 
 
 def random_string(
@@ -40,6 +40,7 @@ def tmp_mongo_db(request):
     @request.addfinalizer
     def teardown():
         client.drop_database(tmp_mongo_db_name)
+        client.close()
 
     return tmp_mongo_db_name