Added browser chat example (#4022)

std/examples/chat/server_test.ts

@@ -0,0 +1,46 @@
+import { assert, assertEquals } from "../../testing/asserts.ts";
+import { TextProtoReader } from "../../textproto/mod.ts";
+import { BufReader } from "../../io/bufio.ts";
+import { connectWebSocket, WebSocket } from "../../ws/mod.ts";
+
+let server: Deno.Process | undefined;
+async function startServer(): Promise<void> {
+  server = Deno.run({
+    args: [Deno.execPath(), "--allow-net", "--allow-read", "server.ts"],
+    cwd: "examples/chat",
+    stdout: "piped"
+  });
+  try {
+    assert(server.stdout != null);
+    const r = new TextProtoReader(new BufReader(server.stdout));
+    const s = await r.readLine();
+    assert(s !== Deno.EOF && s.includes("chat server starting"));
+  } catch {
+    server.close();
+  }
+}
+
+const { test } = Deno;
+
+await startServer();
+
+test("GET / should serve html", async () => {
+  const resp = await fetch("http://0.0.0.0:8080/");
+  assertEquals(resp.status, 200);
+  assertEquals(resp.headers.get("content-type"), "text/html");
+  const html = await resp.body.text();
+  assert(html.includes("ws chat example"), "body is ok");
+});
+
+let ws: WebSocket | undefined;
+test("GET /ws should upgrade conn to ws", async () => {
+  ws = await connectWebSocket("http://0.0.0.0:8080/ws");
+  const it = ws.receive();
+  assertEquals((await it.next()).value, "Connected: [1]");
+  ws.send("Hello");
+  assertEquals((await it.next()).value, "[1]: Hello");
+});
+test("afterAll", () => {
+  server?.close();
+  ws?.conn.close();
+});