test for stateless apps (#3816)

* test for stateless apps

* add playwright to dev dependencies

* fix docstring

* fix install of playwright in CI

* fix install again

* add allowed license

* add retry on running integrations step

* another attempt to fix licensing issue

* update timeout duration for retry

* fix timeout workflows

* remove dep changes

* remove outdated diff

* fix scope in new test and workflow for appharness

* run playwright tests last

.github/workflows/integration_app_harness.yml

@@ -51,6 +51,7 @@ jobs:
           SCREENSHOT_DIR: /tmp/screenshots
           REDIS_URL: ${{ matrix.state_manager == 'redis' && 'redis://localhost:6379' || '' }}
         run: |
+          poetry run playwright install --with-deps
           poetry run pytest tests/integration
       - uses: actions/upload-artifact@v4
         name: Upload failed test screenshots

tests/integration/tests_playwright/test_stateless_app.py

@@ -0,0 +1,59 @@
+"""Integration tests for a stateless app."""
+
+from typing import Generator
+
+import httpx
+import pytest
+from playwright.sync_api import Page, expect
+
+import reflex as rx
+from reflex.testing import AppHarness
+
+
+def StatelessApp():
+    """A stateless app that renders a heading."""
+    import reflex as rx
+
+    def index():
+        return rx.heading("This is a stateless app")
+
+    app = rx.App()
+    app.add_page(index)
+
+
+@pytest.fixture(scope="module")
+def stateless_app(tmp_path_factory) -> Generator[AppHarness, None, None]:
+    """Create a stateless app AppHarness.
+
+    Args:
+        tmp_path_factory: pytest fixture for creating temporary directories.
+
+    Yields:
+        AppHarness: A harness for testing the stateless app.
+    """
+    with AppHarness.create(
+        root=tmp_path_factory.mktemp("stateless_app"),
+        app_source=StatelessApp,  # type: ignore
+    ) as harness:
+        yield harness
+
+
+def test_statelessness(stateless_app: AppHarness, page: Page):
+    """Test that the stateless app renders a heading but backend/_event is not mounted.
+
+    Args:
+        stateless_app: A harness for testing the stateless app.
+        page: A Playwright page.
+    """
+    assert stateless_app.frontend_url is not None
+    assert stateless_app.backend is not None
+    assert stateless_app.backend.started
+
+    res = httpx.get(rx.config.get_config().api_url + "/_event")
+    assert res.status_code == 404
+
+    res2 = httpx.get(rx.config.get_config().api_url + "/ping")
+    assert res2.status_code == 200
+
+    page.goto(stateless_app.frontend_url)
+    expect(page.get_by_role("heading")).to_have_text("This is a stateless app")