Revised the test site to use the secret key specified in the environment variables when possible, so that the secret key and session keeps in the development environment.

tests/testsite/__init__.py

@@ -17,6 +17,7 @@
 """The Mia! Accounting Flask demonstration website.
 
 """
+import os
 import typing as t
 from secrets import token_urlsafe
 
@@ -45,7 +46,7 @@ def create_app(is_testing: bool = False) -> Flask:
     app: Flask = Flask(__name__)
     db_uri: str = "sqlite:///" if is_testing else "sqlite:///local.sqlite"
     app.config.from_mapping({
-        "SECRET_KEY": token_urlsafe(32),
+        "SECRET_KEY": os.environ.get("SECRET_KEY", token_urlsafe(32)),
         "SQLALCHEMY_DATABASE_URI": db_uri,
         "BABEL_DEFAULT_LOCALE": "en",
         "ALL_LINGUAS": "zh_Hant|正體中文,en|English,zh_Hans|简体中文",