From 7be9b5ace8e597070e85b2b1b8eb44e1bb9efe5f Mon Sep 17 00:00:00 2001
From: "dayuan.jiang" <jdy.toh@gmail.com>
Date: Sun, 11 Oct 2026 13:04:48 +0900
Subject: [PATCH] test(mcp-server): open the built shell with playwright

npm run test:e2e starts dist/index.js over the MCP SDK with
DRAWIO_PREVIEW_UI=shell, opens the URL start_session returns in headless
Chromium, and checks that the bundled draw.io loads without console
errors and that the theme toggle switches draw.io in place.
---
 packages/mcp-server/playwright.config.ts    |  16 +++
 packages/mcp-server/tests/e2e/shell.spec.ts | 113 ++++++++++++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 packages/mcp-server/playwright.config.ts
 create mode 100644 packages/mcp-server/tests/e2e/shell.spec.ts

diff --git a/packages/mcp-server/playwright.config.ts b/packages/mcp-server/playwright.config.ts
new file mode 100644
index 00000000..59dfba86
--- /dev/null
+++ b/packages/mcp-server/playwright.config.ts
@@ -0,0 +1,16 @@
+import { defineConfig } from "@playwright/test"
+
+// Browser tests of the built package (npm run build first): each spec
+// starts the MCP server itself over stdio, so there is no web server here.
+// Playwright comes from the repository root (npm ci there).
+export default defineConfig({
+    testDir: "./tests/e2e",
+    timeout: 90_000,
+    forbidOnly: !!process.env.CI,
+    retries: process.env.CI ? 1 : 0,
+    reporter: "list",
+    use: {
+        browserName: "chromium",
+        trace: "retain-on-failure",
+    },
+})
diff --git a/packages/mcp-server/tests/e2e/shell.spec.ts b/packages/mcp-server/tests/e2e/shell.spec.ts
new file mode 100644
index 00000000..1e446104
--- /dev/null
+++ b/packages/mcp-server/tests/e2e/shell.spec.ts
@@ -0,0 +1,113 @@
+/**
+ * The canvas shell as start_session opens it with DRAWIO_PREVIEW_UI=shell:
+ * the built server (dist/index.js) runs over stdio as an MCP client would
+ * start it, and headless Chromium opens the URL it returns.
+ */
+import { mkdtempSync, rmSync } from "node:fs"
+import { tmpdir } from "node:os"
+import { dirname, join } from "node:path"
+import { fileURLToPath } from "node:url"
+import { Client } from "@modelcontextprotocol/sdk/client/index.js"
+import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js"
+import { expect, test } from "@playwright/test"
+
+const pkg = join(dirname(fileURLToPath(import.meta.url)), "../..")
+
+let client: Client
+let dataDir: string
+let shellUrl: string
+
+test.beforeAll(async () => {
+    dataDir = mkdtempSync(join(tmpdir(), "mcp-shell-e2e-"))
+    const transport = new StdioClientTransport({
+        command: process.execPath,
+        args: [join(pkg, "dist/index.js")],
+        env: {
+            ...process.env,
+            DRAWIO_DATA_DIR: dataDir,
+            DRAWIO_PREVIEW_UI: "shell",
+            // Away from the web app's dev server and other test runs
+            PORT: String(6100 + Math.floor(Math.random() * 400)),
+            BROWSER: "none",
+        },
+        stderr: "pipe",
+    })
+    client = new Client({ name: "shell-e2e", version: "0.0.1" })
+    await client.connect(transport)
+    const result = await client.callTool({
+        name: "start_session",
+        arguments: {},
+    })
+    const text = (result.content as { type: string; text?: string }[])
+        .map((c) => c.text ?? "")
+        .join("\n")
+    const match = text.match(/Browser URL: (\S+)/)
+    if (!match) throw new Error(`start_session gave no URL:\n${text}`)
+    shellUrl = match[1]
+})
+
+test.afterAll(async () => {
+    await client?.close()
+    rmSync(dataDir, { recursive: true, force: true })
+})
+
+test("start_session opens the shell, which loads the bundled draw.io", async ({
+    page,
+}) => {
+    expect(shellUrl).toMatch(/^http:\/\/localhost:\d+\/shell\/\?mcp=mcp-/)
+    const errors: string[] = []
+    page.on("console", (message) => {
+        if (message.type() === "error") errors.push(message.text())
+    })
+    page.on("pageerror", (error) => errors.push(error.message))
+
+    await page.goto(shellUrl)
+    const iframe = page.locator("iframe[title='draw.io']")
+    await expect(iframe).toHaveAttribute(
+        "src",
+        /^http:\/\/localhost:\d+\/drawio\/index\.html\?embed=1&proto=json&configure=1&/,
+    )
+    // The cover goes once draw.io sent "init" and loaded the first document
+    await expect(page.getByTestId("canvas-loading")).toHaveCount(0, {
+        timeout: 60_000,
+    })
+    const frame = page.frameLocator("iframe[title='draw.io']")
+    await expect(frame.locator(".geDiagramContainer")).toBeVisible()
+
+    // The shell's own texts and state
+    await expect(page.getByTestId("shell-status")).toHaveText(
+        "Waiting for the MCP server…",
+    )
+    await expect(page.getByTestId("shell-session")).toHaveText(
+        shellUrl.slice(-8),
+    )
+    expect(errors).toEqual([])
+})
+
+test("the theme toggle switches the page and draw.io, and is remembered", async ({
+    page,
+}) => {
+    await page.goto(shellUrl)
+    await expect(page.getByTestId("canvas-loading")).toHaveCount(0, {
+        timeout: 60_000,
+    })
+    const html = page.locator("html")
+    const frameBody = page
+        .frameLocator("iframe[title='draw.io']")
+        .locator("body")
+    await expect(html).not.toHaveClass(/dark/)
+    await expect(frameBody).not.toHaveClass(/geDarkMode/)
+
+    await page.getByTestId("theme-toggle").click()
+    await expect(html).toHaveClass(/dark/)
+    // Same-origin draw.io switches in place, without a reload
+    await expect(frameBody).toHaveClass(/geDarkMode/)
+    expect(
+        await page.evaluate(() => localStorage.getItem("mcp:dark-mode")),
+    ).toBe("true")
+
+    await page.reload()
+    await expect(html).toHaveClass(/dark/)
+    await page.getByTestId("theme-toggle").click()
+    await expect(html).not.toHaveClass(/dark/)
+})