Add docker container prober

tests/probers/docker.spec.ts

@@ -0,0 +1,36 @@
+import {expect, test} from '@playwright/test';
+
+/**
+ * Prober: Docker container
+ *
+ * Pulls the Docker image published to GHCR, runs it locally with the test
+ * GEDCOM file mounted via STATIC_URL, and verifies that the containerized
+ * application starts and renders data. This exercises the Docker build path
+ * (multi-stage Dockerfile, Caddy server configuration, static URL template
+ * injection) and confirms the published container image is functional.
+ *
+ * The workflow starts the container externally (via `docker run`) before
+ * this test runs, so Playwright connects to localhost:8080 directly.
+ */
+test('Docker container prober', async ({page}) => {
+  await page.goto('http://localhost:8080/');
+
+  // Wait for the app to reach SHOWING_CHART state.
+  await expect(page.locator('#content')).toBeVisible();
+
+  // Assert the expected person's name appears in the chart SVG.
+  await expect(page.locator('#chart')).toContainText('Bonifacy');
+
+  // Assert the expected person's name appears in the side panel.
+  // Scoped to div.details to avoid matching <text class="details sex"> SVG
+  // elements in the chart that also carry the "details" class.
+  await expect(page.locator('div.details')).toContainText('Bonifacy');
+
+  // Assert no fatal error is displayed (replaces chart when state is ERROR).
+  await expect(page.locator('.ui.error.message')).not.toBeVisible();
+
+  // Assert no popup error is displayed.
+  // ErrorPopup uses Semantic UI React's <Portal>, which renders at
+  // document.body level, not inside #content.
+  await expect(page.locator('.ui.errorPopup.message')).not.toBeVisible();
+});