viz browser tests (#10626)

* viz browser tests

* expect failure if js/ isn't included

* back green

test/web/test_viz.js

@@ -0,0 +1,34 @@
+const { spawn } = require("child_process");
+const puppeteer = require("puppeteer");
+
+async function main() {
+  // ** start viz server
+  const proc = spawn("python", ["-u", "-c", "from tinygrad import Tensor; Tensor.arange(4).realize()"], { env: { ...process.env, VIZ:"1" },
+                      stdio: ["inherit", "pipe", "inherit"]});
+  await new Promise(resolve => proc.stdout.on("data", r => {
+    if (r.includes("ready")) resolve();
+  }));
+
+  // ** run browser tests
+  let browser;
+  try {
+    browser = await puppeteer.launch({ headless: true });
+    const page = await browser.newPage();
+    const res = await page.goto("http://localhost:8000");
+    if (res.status() !== 200) throw new Error("Failed to load page");
+    const scheduleSelector = await page.waitForSelector("ul");
+    scheduleSelector.click();
+    await page.waitForSelector("rect");
+    const nodes = await page.evaluate(() => document.querySelectorAll("#nodes > g").length);
+    const edges = await page.evaluate(() => document.querySelectorAll("#edges > path").length);
+    if (!nodes || !edges) {
+      throw new Error("VIZ didn't render a graph")
+    }
+  } finally {
+    // ** cleanups
+    if (browser) await browser.close();
+    proc.kill();
+  }
+}
+
+main();