add example code for testing typing tools

tests/typing/typing_route.py

@@ -0,0 +1,53 @@
+from http import HTTPStatus
+from typing import Tuple
+from typing import Union
+
+from flask import Flask
+from flask import jsonify
+from flask.templating import render_template
+from flask.views import View
+from flask.wrappers import Response
+
+
+app = Flask(__name__)
+
+
+@app.route("/")
+def hello_world() -> str:
+    return "<p>Hello, World!</p>"
+
+
+@app.route("/json")
+def hello_world_json() -> Response:
+    return jsonify({"response": "Hello, World!"})
+
+
+@app.route("/template")
+@app.route("/template/<name>")
+def return_template(name: Union[str, None] = None) -> str:
+    return render_template("index.html", name=name)
+
+
+@app.errorhandler(HTTPStatus.INTERNAL_SERVER_ERROR)
+def error_500(e) -> Tuple[str, int]:
+    return "<p>Sorry, we are having problems</p>", HTTPStatus.INTERNAL_SERVER_ERROR
+
+
+@app.before_request
+def before_request() -> None:
+    app.logger.debug("Executing a sample before_request function")
+    return None
+
+
+class RenderTemplateView(View):
+    def __init__(self: "RenderTemplateView", template_name: str) -> None:
+        self.template_name = template_name
+
+    def dispatch_request(self: "RenderTemplateView") -> str:
+        return render_template(self.template_name)
+
+
+app.add_url_rule(
+    "/about",
+    view_func=RenderTemplateView.as_view("about_page", template_name="about.html"),
+)