pythongh-124621: Emscripten: Add smoke test for using pyrepl in Chrome (python#137004)

Adds a mechanism to test browser-based initialisation of the Python interpreter,
via a Playwright headless browser instance.

Author: hoodmane

Tools/wasm/README.md

@@ -84,6 +84,17 @@ make a node application that "embeds" the interpreter instead of acting like the
 CLI you will need to write your own alternative to `node_entry.mjs`.
 
 
+### Running tests
+
+After building, you can run the full test suite with:
+```shell
+./cross-build/wasm32-emscripten/build/python/python.sh -m test -uall
+```
+You can run the browser smoke test with:
+```shell
+./Tools/wasm/emscripten/browser_test/run_test.sh
+```
+
 ### The Web Example
 
 When building for Emscripten, the web example will be built automatically. It

Tools/wasm/emscripten/browser_test/.gitignore

@@ -0,0 +1,4 @@
+node_modules
+test-results
+playwright-report
+test_log.txt

Tools/wasm/emscripten/browser_test/index.spec.ts

@@ -0,0 +1,15 @@
+import { test, expect } from '@playwright/test';
+
+test('has title', async ({ page }) => {
+  await page.goto('/');
+
+  await expect(page).toHaveTitle("Emscripten PyRepl Example");
+  const xterm = await page.locator('css=#terminal');
+  await expect(xterm).toHaveText(/Python.*on emscripten.*Type.*for more information/);
+  const xtermInput = await page.getByRole('textbox');
+  await xtermInput.pressSequentially(`def f():\nprint("hello", "emscripten repl!")\n\n`);
+  await xtermInput.pressSequentially(`f()\n`);
+  await expect(xterm).toHaveText(/hello emscripten repl!/);
+
+});
+