diff --git a/sanic/app.py b/sanic/app.py
index da171867..c471855b 100644
--- a/sanic/app.py
+++ b/sanic/app.py
@@ -826,6 +826,14 @@ class Sanic:
                 "Endpoint with name `{}` was not found".format(view_name)
             )
 
+        # If the route has host defined, split that off
+        # TODO: Retain netloc and path separately in Route objects
+        host = uri.find("/")
+        if host > 0:
+            host, uri = uri[:host], uri[host:]
+        else:
+            host = None
+
         if view_name == "static" or view_name.endswith(".static"):
             filename = kwargs.pop("filename", None)
             # it's static folder
@@ -858,7 +866,7 @@ class Sanic:
 
         netloc = kwargs.pop("_server", None)
         if netloc is None and external:
-            netloc = self.config.get("SERVER_NAME", "")
+            netloc = host or self.config.get("SERVER_NAME", "")
 
         if external:
             if not scheme:
diff --git a/tests/conftest.py b/tests/conftest.py
index d720f3be..5c217cdd 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -103,7 +103,7 @@ def sanic_router():
         for method, route in route_details:
             try:
                 router._add(
-                    uri="/{}".format(route),
+                    uri=f"/{route}",
                     methods=frozenset({method}),
                     host="localhost",
                     handler=_handler,
diff --git a/tests/test_app.py b/tests/test_app.py
index 6f79ef22..f639d9f3 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -179,9 +179,7 @@ def test_handle_request_with_nested_exception_debug(app, monkeypatch):
     request, response = app.test_client.get("/", debug=True)
     assert response.status == 500
     assert response.text.startswith(
-        "Error while handling error: {}\nStack: Traceback (most recent call last):\n".format(
-            err_msg
-        )
+        f"Error while handling error: {err_msg}\nStack: Traceback (most recent call last):\n"
     )
 
 
diff --git a/tests/test_blueprint_group.py b/tests/test_blueprint_group.py
index 5a4b805c..813ec2ff 100644
--- a/tests/test_blueprint_group.py
+++ b/tests/test_blueprint_group.py
@@ -40,9 +40,9 @@ def test_bp_group_with_additional_route_params(app: Sanic):
     )
     def blueprint_2_named_method(request: Request, param):
         if request.method == "DELETE":
-            return text("DELETE_{}".format(param))
+            return text(f"DELETE_{param}")
         elif request.method == "PATCH":
-            return text("PATCH_{}".format(param))
+            return text(f"PATCH_{param}")
 
     blueprint_group = Blueprint.group(
         blueprint_1, blueprint_2, url_prefix="/api"
diff --git a/tests/test_blueprints.py b/tests/test_blueprints.py
index 55353efa..e65ba8f2 100644
--- a/tests/test_blueprints.py
+++ b/tests/test_blueprints.py
@@ -46,19 +46,19 @@ def test_versioned_routes_get(app, method):
     func = getattr(bp, method)
     if callable(func):
 
-        @func("/{}".format(method), version=1)
+        @func(f"/{method}", version=1)
         def handler(request):
             return text("OK")
 
     else:
         print(func)
-        raise Exception("{} is not callable".format(func))
+        raise Exception(f"{func} is not callable")
 
     app.blueprint(bp)
 
     client_method = getattr(app.test_client, method)
 
-    request, response = client_method("/v1/{}".format(method))
+    request, response = client_method(f"/v1/{method}")
     assert response.status == 200
 
 
@@ -543,7 +543,7 @@ def test_bp_group_with_default_url_prefix(app):
 
     resource_id = str(uuid4())
     request, response = app.test_client.get(
-        "/api/v1/resources/{0}".format(resource_id)
+        f"/api/v1/resources/{resource_id}"
     )
     assert response.json == {"resource_id": resource_id}
 
@@ -658,9 +658,9 @@ def test_duplicate_blueprint(app):
         app.blueprint(bp1)
 
     assert str(excinfo.value) == (
-        'A blueprint with the name "{}" is already registered.  '
+        f'A blueprint with the name "{bp_name}" is already registered.  '
         "Blueprint names must be unique."
-    ).format(bp_name)
+    )
 
 
 @pytest.mark.parametrize("debug", [True, False, None])
diff --git a/tests/test_cookies.py b/tests/test_cookies.py
index 737a752d..74e894c4 100644
--- a/tests/test_cookies.py
+++ b/tests/test_cookies.py
@@ -15,7 +15,8 @@ from sanic.response import text
 def test_cookies(app):
     @app.route("/")
     def handler(request):
-        response = text("Cookies are: {}".format(request.cookies["test"]))
+        cookie_value = request.cookies["test"]
+        response = text(f"Cookies are: {cookie_value}")
         response.cookies["right_back"] = "at you"
         return response
 
@@ -31,7 +32,8 @@ def test_cookies(app):
 async def test_cookies_asgi(app):
     @app.route("/")
     def handler(request):
-        response = text("Cookies are: {}".format(request.cookies["test"]))
+        cookie_value = request.cookies["test"]
+        response = text(f"Cookies are: {cookie_value}")
         response.cookies["right_back"] = "at you"
         return response
 
@@ -78,7 +80,8 @@ def test_false_cookies(app, httponly, expected):
 def test_http2_cookies(app):
     @app.route("/")
     async def handler(request):
-        response = text("Cookies are: {}".format(request.cookies["test"]))
+        cookie_value = request.cookies["test"]
+        response = text(f"Cookies are: {cookie_value}")
         return response
 
     headers = {"cookie": "test=working!"}
diff --git a/tests/test_exceptions_handler.py b/tests/test_exceptions_handler.py
index 57a9e72b..58ea9b58 100644
--- a/tests/test_exceptions_handler.py
+++ b/tests/test_exceptions_handler.py
@@ -43,7 +43,7 @@ def handler_6(request, arg):
     try:
         foo = 1 / arg
     except Exception as e:
-        raise e from ValueError("{}".format(arg))
+        raise e from ValueError(f"{arg}")
     return text(foo)
 
 
diff --git a/tests/test_keep_alive_timeout.py b/tests/test_keep_alive_timeout.py
index a59d6c5b..ec9d9975 100644
--- a/tests/test_keep_alive_timeout.py
+++ b/tests/test_keep_alive_timeout.py
@@ -97,11 +97,9 @@ class ReuseableSanicTestClient(SanicTestClient):
         ):
             url = uri
         else:
-            uri = uri if uri.startswith("/") else "/{uri}".format(uri=uri)
+            uri = uri if uri.startswith("/") else f"/{uri}"
             scheme = "http"
-            url = "{scheme}://{host}:{port}{uri}".format(
-                scheme=scheme, host=HOST, port=PORT, uri=uri
-            )
+            url = f"{scheme}://{HOST}:{PORT}{uri}"
 
         @self.app.listener("after_server_start")
         async def _collect_response(loop):
@@ -134,7 +132,7 @@ class ReuseableSanicTestClient(SanicTestClient):
         self.app.listeners["after_server_start"].pop()
 
         if exceptions:
-            raise ValueError("Exception during request: {}".format(exceptions))
+            raise ValueError(f"Exception during request: {exceptions}")
 
         if gather_request:
             self.app.request_middleware.pop()
@@ -143,16 +141,14 @@ class ReuseableSanicTestClient(SanicTestClient):
                 return request, response
             except Exception:
                 raise ValueError(
-                    "Request and response object expected, got ({})".format(
-                        results
-                    )
+                    f"Request and response object expected, got ({results})"
                 )
         else:
             try:
                 return results[-1]
             except Exception:
                 raise ValueError(
-                    "Request object expected, got ({})".format(results)
+                    f"Request object expected, got ({results})"
                 )
 
     def kill_server(self):
diff --git a/tests/test_logo.py b/tests/test_logo.py
index 2f9cb90f..0c34cdb5 100644
--- a/tests/test_logo.py
+++ b/tests/test_logo.py
@@ -52,7 +52,7 @@ def test_logo_false(app, caplog):
     assert caplog.record_tuples[ROW][1] == logging.INFO
     assert caplog.record_tuples[ROW][
         2
-    ] == "Goin' Fast @ http://127.0.0.1:{}".format(PORT)
+    ] == f"Goin' Fast @ http://127.0.0.1:{PORT}"
 
 
 def test_logo_true(app, caplog):
diff --git a/tests/test_named_routes.py b/tests/test_named_routes.py
index 29b8e40d..0eacf4cc 100644
--- a/tests/test_named_routes.py
+++ b/tests/test_named_routes.py
@@ -21,13 +21,13 @@ def test_versioned_named_routes_get(app, method):
     bp = Blueprint("test_bp", url_prefix="/bp")
 
     method = method.lower()
-    route_name = "route_{}".format(method)
-    route_name2 = "route2_{}".format(method)
+    route_name = f"route_{method}"
+    route_name2 = f"route2_{method}"
 
     func = getattr(app, method)
     if callable(func):
 
-        @func("/{}".format(method), version=1, name=route_name)
+        @func(f"/{method}", version=1, name=route_name)
         def handler(request):
             return text("OK")
 
@@ -38,7 +38,7 @@ def test_versioned_named_routes_get(app, method):
     func = getattr(bp, method)
     if callable(func):
 
-        @func("/{}".format(method), version=1, name=route_name2)
+        @func(f"/{method}", version=1, name=route_name2)
         def handler2(request):
             return text("OK")
 
@@ -48,14 +48,14 @@ def test_versioned_named_routes_get(app, method):
 
     app.blueprint(bp)
 
-    assert app.router.routes_all["/v1/{}".format(method)].name == route_name
+    assert app.router.routes_all[f"/v1/{method}"].name == route_name
 
-    route = app.router.routes_all["/v1/bp/{}".format(method)]
-    assert route.name == "test_bp.{}".format(route_name2)
+    route = app.router.routes_all[f"/v1/bp/{method}"]
+    assert route.name == f"test_bp.{route_name2}"
 
-    assert app.url_for(route_name) == "/v1/{}".format(method)
-    url = app.url_for("test_bp.{}".format(route_name2))
-    assert url == "/v1/bp/{}".format(method)
+    assert app.url_for(route_name) == f"/v1/{method}"
+    url = app.url_for(f"test_bp.{route_name2}")
+    assert url == f"/v1/bp/{method}"
     with pytest.raises(URLBuildError):
         app.url_for("handler")
 
diff --git a/tests/test_redirect.py b/tests/test_redirect.py
index 7d0c0edf..6bfb2fe3 100644
--- a/tests/test_redirect.py
+++ b/tests/test_redirect.py
@@ -115,14 +115,14 @@ def test_redirect_with_params(app, test_str):
 
     @app.route("/api/v1/test/<test>/")
     async def init_handler(request, test):
-        return redirect("/api/v2/test/{}/".format(use_in_uri))
+        return redirect(f"/api/v2/test/{use_in_uri}/")
 
     @app.route("/api/v2/test/<test>/")
     async def target_handler(request, test):
         assert test == test_str
         return text("OK")
 
-    _, response = app.test_client.get("/api/v1/test/{}/".format(use_in_uri))
+    _, response = app.test_client.get(f"/api/v1/test/{use_in_uri}/")
     assert response.status == 200
 
     assert response.content == b"OK"
diff --git a/tests/test_requests.py b/tests/test_requests.py
index e5abb34f..c1dbd1a3 100644
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -44,7 +44,7 @@ async def test_sync_asgi(app):
 def test_ip(app):
     @app.route("/")
     def handler(request):
-        return text("{}".format(request.ip))
+        return text(f"{request.ip}")
 
     request, response = app.test_client.get("/")
 
@@ -55,7 +55,7 @@ def test_ip(app):
 async def test_ip_asgi(app):
     @app.route("/")
     def handler(request):
-        return text("{}".format(request.url))
+        return text(f"{request.url}")
 
     request, response = await app.asgi_client.get("/")
 
@@ -325,7 +325,7 @@ def test_token(app):
     token = "a1d895e0-553a-421a-8e22-5ff8ecb48cbf"
     headers = {
         "content-type": "application/json",
-        "Authorization": "{}".format(token),
+        "Authorization": f"{token}",
     }
 
     request, response = app.test_client.get("/", headers=headers)
@@ -335,7 +335,7 @@ def test_token(app):
     token = "a1d895e0-553a-421a-8e22-5ff8ecb48cbf"
     headers = {
         "content-type": "application/json",
-        "Authorization": "Token {}".format(token),
+        "Authorization": f"Token {token}",
     }
 
     request, response = app.test_client.get("/", headers=headers)
@@ -345,7 +345,7 @@ def test_token(app):
     token = "a1d895e0-553a-421a-8e22-5ff8ecb48cbf"
     headers = {
         "content-type": "application/json",
-        "Authorization": "Bearer {}".format(token),
+        "Authorization": f"Bearer {token}",
     }
 
     request, response = app.test_client.get("/", headers=headers)
@@ -370,7 +370,7 @@ async def test_token_asgi(app):
     token = "a1d895e0-553a-421a-8e22-5ff8ecb48cbf"
     headers = {
         "content-type": "application/json",
-        "Authorization": "{}".format(token),
+        "Authorization": f"{token}",
     }
 
     request, response = await app.asgi_client.get("/", headers=headers)
@@ -380,7 +380,7 @@ async def test_token_asgi(app):
     token = "a1d895e0-553a-421a-8e22-5ff8ecb48cbf"
     headers = {
         "content-type": "application/json",
-        "Authorization": "Token {}".format(token),
+        "Authorization": f"Token {token}",
     }
 
     request, response = await app.asgi_client.get("/", headers=headers)
@@ -390,7 +390,7 @@ async def test_token_asgi(app):
     token = "a1d895e0-553a-421a-8e22-5ff8ecb48cbf"
     headers = {
         "content-type": "application/json",
-        "Authorization": "Bearer {}".format(token),
+        "Authorization": f"Bearer {token}",
     }
 
     request, response = await app.asgi_client.get("/", headers=headers)
@@ -1028,7 +1028,7 @@ def test_url_attributes_no_ssl(app, path, query, expected_url):
 
     app.add_route(handler, path)
 
-    request, response = app.test_client.get(path + "?{}".format(query))
+    request, response = app.test_client.get(path + f"?{query}")
     assert request.url == expected_url.format(HOST, PORT)
 
     parsed = urlparse(request.url)
@@ -1054,7 +1054,7 @@ async def test_url_attributes_no_ssl_asgi(app, path, query, expected_url):
 
     app.add_route(handler, path)
 
-    request, response = await app.asgi_client.get(path + "?{}".format(query))
+    request, response = await app.asgi_client.get(path + f"?{query}")
     assert request.url == expected_url.format(ASGI_HOST)
 
     parsed = urlparse(request.url)
@@ -1087,7 +1087,7 @@ def test_url_attributes_with_ssl_context(app, path, query, expected_url):
     app.add_route(handler, path)
 
     request, response = app.test_client.get(
-        "https://{}:{}".format(HOST, PORT) + path + "?{}".format(query),
+        f"https://{HOST}:{PORT}" + path + f"?{query}",
         server_kwargs={"ssl": context},
     )
     assert request.url == expected_url.format(HOST, PORT)
@@ -1122,7 +1122,7 @@ def test_url_attributes_with_ssl_dict(app, path, query, expected_url):
     app.add_route(handler, path)
 
     request, response = app.test_client.get(
-        "https://{}:{}".format(HOST, PORT) + path + "?{}".format(query),
+        f"https://{HOST}:{PORT}" + path + f"?{query}",
         server_kwargs={"ssl": ssl_dict},
     )
     assert request.url == expected_url.format(HOST, PORT)
diff --git a/tests/test_response.py b/tests/test_response.py
index ff23b3b8..b2d5a157 100644
--- a/tests/test_response.py
+++ b/tests/test_response.py
@@ -297,7 +297,7 @@ def test_file_response(app, file_name, static_file_directory, status):
             mime_type=guess_type(file_path)[0] or "text/plain",
         )
 
-    request, response = app.test_client.get("/files/{}".format(file_name))
+    request, response = app.test_client.get(f"/files/{file_name}")
     assert response.status == status
     assert response.body == get_file_content(static_file_directory, file_name)
     assert "Content-Disposition" not in response.headers
@@ -320,12 +320,12 @@ def test_file_response_custom_filename(
         file_path = os.path.abspath(unquote(file_path))
         return file(file_path, filename=dest)
 
-    request, response = app.test_client.get("/files/{}".format(source))
+    request, response = app.test_client.get(f"/files/{source}")
     assert response.status == 200
     assert response.body == get_file_content(static_file_directory, source)
     assert response.headers[
         "Content-Disposition"
-    ] == 'attachment; filename="{}"'.format(dest)
+    ] == f'attachment; filename="{dest}"'
 
 
 @pytest.mark.parametrize("file_name", ["test.file", "decode me.txt"])
@@ -350,7 +350,7 @@ def test_file_head_response(app, file_name, static_file_directory):
                 mime_type=guess_type(file_path)[0] or "text/plain",
             )
 
-    request, response = app.test_client.head("/files/{}".format(file_name))
+    request, response = app.test_client.head(f"/files/{file_name}")
     assert response.status == 200
     assert "Accept-Ranges" in response.headers
     assert "Content-Length" in response.headers
@@ -373,7 +373,7 @@ def test_file_stream_response(app, file_name, static_file_directory):
             mime_type=guess_type(file_path)[0] or "text/plain",
         )
 
-    request, response = app.test_client.get("/files/{}".format(file_name))
+    request, response = app.test_client.get(f"/files/{file_name}")
     assert response.status == 200
     assert response.body == get_file_content(static_file_directory, file_name)
     assert "Content-Disposition" not in response.headers
@@ -396,12 +396,12 @@ def test_file_stream_response_custom_filename(
         file_path = os.path.abspath(unquote(file_path))
         return file_stream(file_path, chunk_size=32, filename=dest)
 
-    request, response = app.test_client.get("/files/{}".format(source))
+    request, response = app.test_client.get(f"/files/{source}")
     assert response.status == 200
     assert response.body == get_file_content(static_file_directory, source)
     assert response.headers[
         "Content-Disposition"
-    ] == 'attachment; filename="{}"'.format(dest)
+    ] == f'attachment; filename="{dest}"'
 
 
 @pytest.mark.parametrize("file_name", ["test.file", "decode me.txt"])
@@ -429,7 +429,7 @@ def test_file_stream_head_response(app, file_name, static_file_directory):
                 mime_type=guess_type(file_path)[0] or "text/plain",
             )
 
-    request, response = app.test_client.head("/files/{}".format(file_name))
+    request, response = app.test_client.head(f"/files/{file_name}")
     assert response.status == 200
     # A HEAD request should never be streamed/chunked.
     if "Transfer-Encoding" in response.headers:
@@ -467,13 +467,10 @@ def test_file_stream_response_range(
             _range=range,
         )
 
-    request, response = app.test_client.get("/files/{}".format(file_name))
-    print(response.body)
+    request, response = app.test_client.get(f"/files/{file_name}")
     assert response.status == 206
     assert "Content-Range" in response.headers
-    assert response.headers["Content-Range"] == "bytes {}-{}/{}".format(
-        range.start, range.end, range.total
-    )
+    assert response.headers["Content-Range"] == f"bytes {range.start}-{range.end}/{range.total}"
 
 
 def test_raw_response(app):
diff --git a/tests/test_routes.py b/tests/test_routes.py
index 9c4d36a6..ba2dd617 100644
--- a/tests/test_routes.py
+++ b/tests/test_routes.py
@@ -20,17 +20,17 @@ def test_versioned_routes_get(app, method):
     func = getattr(app, method)
     if callable(func):
 
-        @func("/{}".format(method), version=1)
+        @func(f"/{method}", version=1)
         def handler(request):
             return text("OK")
 
     else:
         print(func)
-        raise Exception("Method: {} is not callable".format(method))
+        raise Exception(f"Method: {method} is not callable")
 
     client_method = getattr(app.test_client, method)
 
-    request, response = client_method("/v1/{}".format(method))
+    request, response = client_method(f"/v1/{method}")
     assert response.status == 200
 
 
@@ -163,7 +163,7 @@ def test_route_optional_slash(app):
 def test_route_strict_slashes_set_to_false_and_host_is_a_list(app):
     # Part of regression test for issue #1120
 
-    site1 = "127.0.0.1:{}".format(app.test_client.port)
+    site1 = f"127.0.0.1:{app.test_client.port}"
 
     # before fix, this raises a RouteExists error
     @app.get("/get", host=[site1, "site2.com"], strict_slashes=False)
@@ -393,7 +393,8 @@ def test_dynamic_route_uuid(app):
     assert response.text == "OK"
     assert type(results[0]) is uuid.UUID
 
-    request, response = app.test_client.get("/quirky/{}".format(uuid.uuid4()))
+    generated_uuid = uuid.uuid4()
+    request, response = app.test_client.get(f"/quirky/{generated_uuid}")
     assert response.status == 200
 
     request, response = app.test_client.get("/quirky/non-existing")
@@ -794,7 +795,7 @@ def test_remove_inexistent_route(app):
     with pytest.raises(RouteDoesNotExist) as excinfo:
         app.remove_route(uri)
 
-    assert str(excinfo.value) == "Route was not registered: {}".format(uri)
+    assert str(excinfo.value) == f"Route was not registered: {uri}"
 
 
 def test_removing_slash(app):
diff --git a/tests/test_server_events.py b/tests/test_server_events.py
index 1a74d960..edc3d00d 100644
--- a/tests/test_server_events.py
+++ b/tests/test_server_events.py
@@ -22,7 +22,7 @@ skipif_no_alarm = pytest.mark.skipif(
 
 def create_listener(listener_name, in_list):
     async def _listener(app, loop):
-        print("DEBUG MESSAGE FOR PYTEST for {}".format(listener_name))
+        print(f"DEBUG MESSAGE FOR PYTEST for {listener_name}")
         in_list.insert(0, app.name + listener_name)
 
     return _listener
diff --git a/tests/test_static.py b/tests/test_static.py
index bd5feb1a..984e22c4 100644
--- a/tests/test_static.py
+++ b/tests/test_static.py
@@ -98,7 +98,7 @@ def test_static_directory(app, file_name, base_uri, static_file_directory):
     app.static(base_uri, static_file_directory)
 
     request, response = app.test_client.get(
-        uri="{}/{}".format(base_uri, file_name)
+        uri=f"{base_uri}/{file_name}"
     )
     assert response.status == 200
     assert response.body == get_file_content(static_file_directory, file_name)
@@ -234,7 +234,7 @@ def test_static_content_range_invalid_unit(
     )
 
     unit = "bit"
-    headers = {"Range": "{}=1-0".format(unit)}
+    headers = {"Range": f"{unit}=1-0"}
     request, response = app.test_client.get("/testing.file", headers=headers)
 
     assert response.status == 416
@@ -252,7 +252,7 @@ def test_static_content_range_invalid_start(
     )
 
     start = "start"
-    headers = {"Range": "bytes={}-0".format(start)}
+    headers = {"Range": f"bytes={start}-0"}
     request, response = app.test_client.get("/testing.file", headers=headers)
 
     assert response.status == 416
@@ -270,7 +270,7 @@ def test_static_content_range_invalid_end(
     )
 
     end = "end"
-    headers = {"Range": "bytes=1-{}".format(end)}
+    headers = {"Range": f"bytes=1-{end}"}
     request, response = app.test_client.get("/testing.file", headers=headers)
 
     assert response.status == 416
@@ -373,7 +373,7 @@ def test_file_not_found(app, static_file_directory):
 def test_static_name(app, static_file_directory, static_name, file_name):
     app.static("/static", static_file_directory, name=static_name)
 
-    request, response = app.test_client.get("/static/{}".format(file_name))
+    request, response = app.test_client.get(f"/static/{file_name}")
 
     assert response.status == 200
 
diff --git a/tests/test_test_client_port.py b/tests/test_test_client_port.py
index 231ec4b5..1b4f300b 100644
--- a/tests/test_test_client_port.py
+++ b/tests/test_test_client_port.py
@@ -1,5 +1,3 @@
-import socket
-
 from sanic.response import json, text
 from sanic.testing import PORT, SanicTestClient
 
diff --git a/tests/test_url_building.py b/tests/test_url_building.py
index 816ce997..81fb8aaa 100644
--- a/tests/test_url_building.py
+++ b/tests/test_url_building.py
@@ -20,30 +20,24 @@ URL_FOR_ARGS3 = dict(
     arg1="v1",
     _anchor="anchor",
     _scheme="http",
-    _server="{}:{}".format(test_host, test_port),
+    _server=f"{test_host}:{test_port}",
     _external=True,
 )
-URL_FOR_VALUE3 = "http://{}:{}/myurl?arg1=v1#anchor".format(
-    test_host, test_port
-)
+URL_FOR_VALUE3 = f"http://{test_host}:{test_port}/myurl?arg1=v1#anchor"
 URL_FOR_ARGS4 = dict(
     arg1="v1",
     _anchor="anchor",
     _external=True,
-    _server="http://{}:{}".format(test_host, test_port),
-)
-URL_FOR_VALUE4 = "http://{}:{}/myurl?arg1=v1#anchor".format(
-    test_host, test_port
+    _server=f"http://{test_host}:{test_port}",
 )
+URL_FOR_VALUE4 = f"http://{test_host}:{test_port}/myurl?arg1=v1#anchor"
 
 
 def _generate_handlers_from_names(app, l):
     for name in l:
         # this is the easiest way to generate functions with dynamic names
         exec(
-            '@app.route(name)\ndef {}(request):\n\treturn text("{}")'.format(
-                name, name
-            )
+            f'@app.route(name)\ndef {name}(request):\n\treturn text("{name}")'
         )
 
 
@@ -60,7 +54,7 @@ def test_simple_url_for_getting(simple_app):
     for letter in string.ascii_letters:
         url = simple_app.url_for(letter)
 
-        assert url == "/{}".format(letter)
+        assert url == f"/{letter}"
         request, response = simple_app.test_client.get(url)
         assert response.status == 200
         assert response.text == letter
@@ -88,7 +82,7 @@ def test_simple_url_for_getting_with_more_params(app, args, url):
 
 def test_url_for_with_server_name(app):
 
-    server_name = "{}:{}".format(test_host, test_port)
+    server_name = f"{test_host}:{test_port}"
     app.config.update({"SERVER_NAME": server_name})
     path = "/myurl"
 
@@ -96,7 +90,7 @@ def test_url_for_with_server_name(app):
     def passes(request):
         return text("this should pass")
 
-    url = "http://{}{}".format(server_name, path)
+    url = f"http://{server_name}{path}"
     assert url == app.url_for("passes", _server=None, _external=True)
     request, response = app.test_client.get(url)
     assert response.status == 200
@@ -118,7 +112,7 @@ def test_fails_url_build_if_param_not_passed(app):
     url = "/"
 
     for letter in string.ascii_letters:
-        url += "<{}>/".format(letter)
+        url += f"<{letter}>/"
 
     @app.route(url)
     def fail(request):
@@ -182,7 +176,7 @@ def test_passes_with_negative_int_message(app):
     @app.route("path/<possibly_neg:int>/another-word")
     def good(request, possibly_neg):
         assert isinstance(possibly_neg, int)
-        return text("this should pass with `{}`".format(possibly_neg))
+        return text(f"this should pass with `{possibly_neg}`")
 
     u_plus_3 = app.url_for("good", possibly_neg=3)
     assert u_plus_3 == "/path/3/another-word", u_plus_3
@@ -237,13 +231,13 @@ def test_passes_with_negative_number_message(app, number):
     @app.route("path/<possibly_neg:number>/another-word")
     def good(request, possibly_neg):
         assert isinstance(possibly_neg, (int, float))
-        return text("this should pass with `{}`".format(possibly_neg))
+        return text(f"this should pass with `{possibly_neg}`")
 
     u = app.url_for("good", possibly_neg=number)
-    assert u == "/path/{}/another-word".format(number), u
+    assert u == f"/path/{number}/another-word", u
     request, response = app.test_client.get(u)
     # For ``number``, it has been cast to a float - so a ``3`` becomes a ``3.0``
-    assert response.text == "this should pass with `{}`".format(float(number))
+    assert response.text == f"this should pass with `{float(number)}`"
 
 
 def test_adds_other_supplied_values_as_query_string(app):
@@ -275,7 +269,7 @@ def blueprint_app(app):
 
     @first_print.route("/foo/<param>")
     def foo_with_param(request, param):
-        return text("foo from first : {}".format(param))
+        return text(f"foo from first : {param}")
 
     @second_print.route("/foo")  # noqa
     def foo(request):
@@ -283,7 +277,7 @@ def blueprint_app(app):
 
     @second_print.route("/foo/<param>")  # noqa
     def foo_with_param(request, param):
-        return text("foo from second : {}".format(param))
+        return text(f"foo from second : {param}")
 
     app.blueprint(first_print)
     app.blueprint(second_print)
diff --git a/tests/test_url_for.py b/tests/test_url_for.py
new file mode 100644
index 00000000..c7e51af1
--- /dev/null
+++ b/tests/test_url_for.py
@@ -0,0 +1,12 @@
+def test_routes_with_host(app):
+    @app.route("/")
+    @app.route("/", name="hostindex", host="example.com")
+    @app.route("/path", name="hostpath", host="path.example.com")
+    def index(request):
+        pass
+
+    assert app.url_for("index") == "/"
+    assert app.url_for("hostindex") == "/"
+    assert app.url_for("hostpath") == "/path"
+    assert app.url_for("hostindex", _external=True) == "http://example.com/"
+    assert app.url_for("hostpath", _external=True) == "http://path.example.com/path"
diff --git a/tests/test_url_for_static.py b/tests/test_url_for_static.py
index f5a426a3..971155ce 100644
--- a/tests/test_url_for_static.py
+++ b/tests/test_url_for_static.py
@@ -118,7 +118,7 @@ def test_static_directory(app, file_name, base_uri, static_file_directory):
     app.static(base_uri2, static_file_directory, name="uploads")
 
     uri = app.url_for("static", name="static", filename=file_name)
-    assert uri == "{}/{}".format(base_uri, file_name)
+    assert uri == f"{base_uri}/{file_name}"
 
     request, response = app.test_client.get(uri)
     assert response.status == 200
@@ -134,7 +134,7 @@ def test_static_directory(app, file_name, base_uri, static_file_directory):
     assert uri2 == uri3
     assert uri3 == uri4
 
-    assert uri5 == "{}/{}".format(base_uri2, file_name)
+    assert uri5 == f"{base_uri2}/{file_name}"
     assert uri5 == uri6
 
     bp = Blueprint("test_bp_static", url_prefix="/bp")
@@ -157,10 +157,10 @@ def test_static_directory(app, file_name, base_uri, static_file_directory):
         "static", name="test_bp_static.uploads", filename="/" + file_name
     )
 
-    assert uri == "/bp{}/{}".format(base_uri, file_name)
+    assert uri == f"/bp{base_uri}/{file_name}"
     assert uri == uri2
 
-    assert uri4 == "/bp{}/{}".format(base_uri2, file_name)
+    assert uri4 == f"/bp{base_uri2}/{file_name}"
     assert uri4 == uri5
 
     request, response = app.test_client.get(uri)
diff --git a/tests/test_views.py b/tests/test_views.py
index c7e3cd5a..f85e5eae 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -147,8 +147,8 @@ def test_with_custom_class_methods(app):
         def get(self, request):
             self._iternal_method()
             return text(
-                "I am get method and global var "
-                "is {}".format(self.global_var)
+                f"I am get method and global var "
+                f"is {self.global_var}"
             )
 
     app.add_route(DummyView.as_view(), "/")