Testing improvements.

dash/testing/application_runners.py

@@ -142,18 +142,20 @@ def __init__(self, keep_open=False, stop_timeout=3):
         super().__init__(keep_open=keep_open, stop_timeout=stop_timeout)
         self.thread = None
 
+    def running_and_accessible(self, url):
+        if self.thread.is_alive():
+            return self.accessible(url)
+        raise DashAppLoadingError("Thread is not alive.")
+
     # pylint: disable=arguments-differ
-    def start(self, app, **kwargs):
+    def start(self, app, start_timeout=3, **kwargs):
         """Start the app server in threading flavor."""
 
         def _handle_error():
             self.stop()
 
         app.server.errorhandler(500)(_handle_error)
 
-        if self.thread and self.thread.is_alive():
-            self.stop()
-
         def run():
             app.scripts.config.serve_locally = True
             app.css.config.serve_locally = True
@@ -170,16 +172,24 @@ def run():
                 app.run(threaded=True, **options)
             except SystemExit:
                 logger.info("Server stopped")
+            except Exception as error:
+                logger.exception(error)
+                raise error
 
         retries = 0
 
         while not self.started and retries < 3:
             try:
+                if self.thread and self.thread.is_alive():
+                    self.stop()
+
                 self.thread = KillerThread(target=run)
                 self.thread.daemon = True
                 self.thread.start()
                 # wait until server is able to answer http request
-                wait.until(lambda: self.accessible(self.url), timeout=2)
+                wait.until(
+                    lambda: self.running_and_accessible(self.url), timeout=start_timeout
+                )
                 self.started = self.thread.is_alive()
             except Exception as err:  # pylint: disable=broad-except
                 logger.exception(err)

dash/testing/plugin.py

@@ -95,33 +95,33 @@ def pytest_runtest_makereport(item, call):  # pylint: disable=unused-argument
 
 
 @pytest.fixture
-def dash_thread_server():
+def dash_thread_server() -> ThreadedRunner:
     """Start a local dash server in a new thread."""
     with ThreadedRunner() as starter:
         yield starter
 
 
 @pytest.fixture
-def dash_process_server():
+def dash_process_server() -> ProcessRunner:
     """Start a Dash server with subprocess.Popen and waitress-serve."""
     with ProcessRunner() as starter:
         yield starter
 
 
 @pytest.fixture
-def dashr_server():
+def dashr_server() -> RRunner:
     with RRunner() as starter:
         yield starter
 
 
 @pytest.fixture
-def dashjl_server():
+def dashjl_server() -> JuliaRunner:
     with JuliaRunner() as starter:
         yield starter
 
 
 @pytest.fixture
-def dash_br(request, tmpdir):
+def dash_br(request, tmpdir) -> Browser:
     with Browser(
         browser=request.config.getoption("webdriver"),
         remote=request.config.getoption("remote"),
@@ -137,7 +137,7 @@ def dash_br(request, tmpdir):
 
 
 @pytest.fixture
-def dash_duo(request, dash_thread_server, tmpdir):
+def dash_duo(request, dash_thread_server, tmpdir) -> DashComposite:
     with DashComposite(
         dash_thread_server,
         browser=request.config.getoption("webdriver"),
@@ -154,7 +154,7 @@ def dash_duo(request, dash_thread_server, tmpdir):
 
 
 @pytest.fixture
-def dashr(request, dashr_server, tmpdir):
+def dashr(request, dashr_server, tmpdir) -> DashRComposite:
     with DashRComposite(
         dashr_server,
         browser=request.config.getoption("webdriver"),
@@ -171,7 +171,7 @@ def dashr(request, dashr_server, tmpdir):
 
 
 @pytest.fixture
-def dashjl(request, dashjl_server, tmpdir):
+def dashjl(request, dashjl_server, tmpdir) -> DashJuliaComposite:
     with DashJuliaComposite(
         dashjl_server,
         browser=request.config.getoption("webdriver"),