Merge pull request #923 from plotly/percy-runner

Percy runner

Author: byronz

dash/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Added
 
+- [#923](https://github.com/plotly/dash/pull/923) Adds one configuration `--percy-assets` in `pytest` to specify extra application assets path if needed
+
 - [#918](https://github.com/plotly/dash/pull/918) Adds `wait_for_element_by_id` and `visit_and_snapshot` APIs in browser, adds `raw_command` option (it also has higher priority than
 the default waitress one) and optional `start_timeout` argument to handle large application within process runner
 

dash/testing/application_runners.py

@@ -216,6 +216,7 @@ def start(
         except (OSError, ValueError):
             logger.exception("process server has encountered an error")
             self.started = False
+            self.stop()
             return
 
         self.started = True

dash/testing/browser.py

@@ -37,8 +37,9 @@ def __init__(
         remote_url=None,
         headless=False,
         options=None,
-        download_path=None,
+        download_path="",
         percy_finalize=True,
+        percy_assets_root="",
         wait_timeout=10,
     ):
         self._browser = browser.lower()
@@ -67,14 +68,17 @@ def __init__(
             loader=percy.ResourceLoader(
                 webdriver=self.driver,
                 base_url="/assets",
-                root_dir="tests/assets",
+                root_dir=percy_assets_root,
             )
         )
         self.percy_runner.initialize_build()
 
-        logger.debug("initialize browser with arguments")
-        logger.debug("  headless => %s", self._headless)
-        logger.debug("  download_path => %s", self._download_path)
+        logger.info("initialize browser with arguments")
+        logger.info("  headless => %s", self._headless)
+        logger.info("  download_path => %s", self._download_path)
+        logger.info(
+            "  percy asset root => %s", os.path.abspath(percy_assets_root)
+        )
 
     def __enter__(self):
         return self
@@ -447,14 +451,21 @@ def reset_log_timestamp(self):
             if entries:
                 self._last_ts = entries[-1]["timestamp"]
 
-    def visit_and_snapshot(self, resource_path, hook_id):
+    def visit_and_snapshot(self, resource_path, hook_id, assert_check=True):
         try:
-            self.driver.get(self.server_url + resource_path)
+            path = resource_path.lstrip('/')
+            if path != resource_path:
+                logger.warning("we stripped the left '/' in resource_path")
+            self.driver.get("{}/{}".format(self.server_url.rstrip('/'), path))
             self.wait_for_element_by_id(hook_id)
-            self.percy_snapshot(resource_path)
+            self.percy_snapshot(path)
+            if assert_check:
+                assert not self.driver.find_elements_by_css_selector(
+                    "div.dash-debug-alert"
+                ), "devtools should not raise an error alert"
             self.driver.back()
         except WebDriverException as e:
-            logger.exception("snapshot at resource %s error", resource_path)
+            logger.exception("snapshot at resource %s error", path)
             raise e
 
     @property

dash/testing/plugin.py

@@ -48,6 +48,13 @@ def pytest_addoption(parser):
         help="set this flag to run in headless mode",
     )
 
+    dash.addoption(
+        "--percy-assets",
+        action="store",
+        default='tests/assets',
+        help="configure how Percy will discover your app's assets"
+    )
+
     dash.addoption(
         "--nopercyfinalize",
         action="store_false",
@@ -117,6 +124,7 @@ def dash_br(request, tmpdir):
         headless=request.config.getoption("headless"),
         options=request.config.hook.pytest_setup_options(),
         download_path=tmpdir.mkdir("download").strpath,
+        percy_assets_root=request.config.getoption("percy_assets"),
         percy_finalize=request.config.getoption("nopercyfinalize"),
     ) as browser:
         yield browser
@@ -132,6 +140,7 @@ def dash_duo(request, dash_thread_server, tmpdir):
         headless=request.config.getoption("headless"),
         options=request.config.hook.pytest_setup_options(),
         download_path=tmpdir.mkdir("download").strpath,
+        percy_assets_root=request.config.getoption("percy_assets"),
         percy_finalize=request.config.getoption("nopercyfinalize"),
     ) as dc:
         yield dc
@@ -147,6 +156,7 @@ def dashr(request, dashr_server, tmpdir):
         headless=request.config.getoption("headless"),
         options=request.config.hook.pytest_setup_options(),
         download_path=tmpdir.mkdir("download").strpath,
+        percy_assets_root=request.config.getoption("percy_assets"),
         percy_finalize=request.config.getoption("nopercyfinalize"),
     ) as dc:
         yield dc