Use a random available port number in tests

CHANGELOG.md

@@ -7,6 +7,7 @@ We follow [Semantic Versions](https://semver.org/).
 
 - Update dependencies
 - Replace `dotty-dict` with `scalpl` to avoid compatibility issues on Windows 10 with Japanese locale
+- Use a random port number for testing the HTTP server (to ensure the port is available)
 
 
 ## Version 0.1.7

tests/conftest.py

@@ -9,6 +9,7 @@
 """
 
 import os
+import socket
 from datetime import datetime
 from typing import Optional
 from unittest import mock
@@ -21,14 +22,23 @@
 
 TEST_ROOT_DIR = os.path.dirname(os.path.abspath(__file__))
 HTTP_SERVER_HOSTNAME = "127.0.0.1"
-HTTP_SERVER_PORT = 65000
 
 OAUTH_CODE = "anime_girls_are_cute"
 REFRESH_TOKEN = "moe_moe_kyun"  # noqa: S105
 
 TEST_IMAGE_URL = "https://raw.githubusercontent.com/slow-start-fans/slow-start-rewatch/master/assets/happy_shion.gif"  # noqa: E501
 
 
+def find_free_tcp_port() -> int:
+    """Return random available port."""
+    with socket.socket() as tcp:
+        tcp.bind((HTTP_SERVER_HOSTNAME, 0))
+        return tcp.getsockname()[1]
+
+
+HTTP_SERVER_PORT = find_free_tcp_port()
+
+
 class MockConfig(Config):
     """
     Simplified version of the Config class.