diff --git a/trolldb/tests/tests_api/test_api.py b/trolldb/tests/tests_api/test_api.py
index 220d993..78150eb 100644
--- a/trolldb/tests/tests_api/test_api.py
+++ b/trolldb/tests/tests_api/test_api.py
@@ -1,4 +1,12 @@
-"""Documentation to be added!"""
+"""Tests for the API server.
+
+Note:
+    The functionalities of the API server is not mocked! For the tests herein an actual API server will be running in a
+    separate process. Moreover, a MongoDB instance is run with databases which are pre-filled with random data having
+    similar characteristics to the real data. Actual requests will be sent to the API and the results will be asserted
+    against expectations.
+"""
+
 import pytest
 from fastapi import status
 
diff --git a/trolldb/tests/tests_database/test_mongodb.py b/trolldb/tests/tests_database/test_mongodb.py
index b25f930..a03b3bd 100644
--- a/trolldb/tests/tests_database/test_mongodb.py
+++ b/trolldb/tests/tests_database/test_mongodb.py
@@ -1,4 +1,10 @@
-"""Direct tests for `mongodb` module without an API server connection."""
+"""Direct tests for :obj:`trolldb.database.mongodb` module without an API server connection.
+
+Note:
+    The functionalities of the MongoDB client is not mocked! For the tests herein an actual MongoDB instance will be
+    run. It includes databases which are pre-filled with random data having similar characteristics to the real data.
+    Actual calls will be made to the running MongoDB instance via the client.
+"""
 
 import errno
 import time