💥 needs more flexible for the arguments, hard to tune waitress with debug mode

Author: byron

Diff for: dash/CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ### Added
 
-- [#918](https://github.com/plotly/dash/pull/918) Adds `wait_for_element_by_id` and `visit_and_snapshot` APIs, adds optional `start_timeout` argument for process runner
+- 💥 [#918](https://github.com/plotly/dash/pull/918) Adds `wait_for_element_by_id` and `visit_and_snapshot` APIs, change the process command options and adds optional `start_timeout` argument for process runner
 
 ### Fixed
 

Diff for: dash/testing/application_runners.py

@@ -180,16 +180,25 @@ def __init__(self, keep_open=False, stop_timeout=3):
 
     # pylint: disable=arguments-differ
     def start(
-        self, app_module, application_name="app", port=8050, start_timeout=3
+        self, waitress_module=None, raw_command=None, port=8050, start_timeout=3
     ):
         """Start the server with waitress-serve in process flavor """
-        entrypoint = "{}:{}.server".format(app_module, application_name)
+        if not (waitress_module or raw_command):  # need to set a least one
+            logging.error(
+                "the process runner needs to start with"
+                " at least one valid command"
+            )
+            return
         self.port = port
-
         args = shlex.split(
-            "waitress-serve --listen=0.0.0.0:{} {}".format(port, entrypoint),
+            raw_command
+            if raw_command
+            else "waitress-serve --listen=0.0.0.0:{} {}".format(
+                port, waitress_module
+            ),
             posix=not self.is_windows,
         )
+
         logger.debug("start dash process with %s", args)
 
         try:

Diff for: tests/unit/test_app_runners.py

@@ -25,7 +25,7 @@ def test_threaded_server_smoke(dash_thread_server):
     sys.version_info < (3,), reason="requires python3 for process testing"
 )
 def test_process_server_smoke(dash_process_server):
-    dash_process_server("simple_app")
+    dash_process_server(waitress_module="simple_app:app.server")
     r = requests.get(dash_process_server.url)
     assert r.status_code == 200, "the server is reachable"
     assert 'id="react-entry-point"' in r.text, "the entrypoint is present"