rwsdk
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Build fast, server-driven webapps on Cloudflare with SSR, RSC, and realtime
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JavaScript
import { describe, expect, it, vi, beforeEach, afterEach } from "vitest";
import { WebSocketServer, WebSocket } from "ws";
import { getSyncedStateClient, onStatusChange, setSyncedStateClientForTesting, __testing, } from "../client-core.js";
const { PENDING_REQUEST_TIMEOUT_MS, getBackoffMs } = __testing;
function wait(ms) {
return new Promise((resolve) => setTimeout(resolve, ms));
}
function waitForOpen(ws) {
return new Promise((resolve, reject) => {
if (ws.readyState === WebSocket.OPEN) {
resolve();
return;
}
const timer = setTimeout(() => reject(new Error("waitForOpen timeout")), 2000);
ws.addEventListener("open", () => {
clearTimeout(timer);
resolve();
});
ws.addEventListener("error", (err) => {
clearTimeout(timer);
reject(err);
});
});
}
function waitForCondition(fn, timeoutMs = 2000) {
return new Promise((resolve, reject) => {
const deadline = Date.now() + timeoutMs;
const check = () => {
const value = fn();
if (value !== undefined) {
resolve(value);
return;
}
if (Date.now() >= deadline) {
reject(new Error("waitForCondition timeout"));
return;
}
setTimeout(check, 10);
};
check();
});
}
function send(ws, message) {
ws.send(JSON.stringify({ v: 1, ...message }));
}
function collectMessages(ws) {
const messages = [];
ws.on("message", (data) => {
messages.push(JSON.parse(data.toString()));
});
return messages;
}
function ackSubscribe(ws, messages, index) {
const msg = messages[index];
if (msg?.kind !== "subscribe") {
throw new Error(`Expected subscribe message at index ${index}`);
}
send(ws, { kind: "subscribe", key: msg.key, id: msg.id });
}
function ackGetState(ws, messages, index, value) {
const msg = messages[index];
if (msg?.kind !== "getState") {
throw new Error(`Expected getState message at index ${index}`);
}
send(ws, { kind: "getState", key: msg.key, value, id: msg.id });
}
describe("client-core", () => {
let wss;
let serverSockets = [];
let serverMessages = [];
let clients = [];
beforeEach(async () => {
vi.useFakeTimers({ shouldAdvanceTime: true });
setSyncedStateClientForTesting(null);
serverSockets = [];
serverMessages = [];
clients = [];
wss = new WebSocketServer({ port: 0 });
wss.on("connection", (ws) => {
serverSockets.push(ws);
serverMessages.push(collectMessages(ws));
});
await wait(10);
});
afterEach(() => {
for (const ws of clients) {
if (ws.readyState === WebSocket.OPEN ||
ws.readyState === WebSocket.CONNECTING) {
ws.close();
}
}
wss.clients.forEach((ws) => ws.close());
wss.close();
setSyncedStateClientForTesting(null);
vi.useRealTimers();
});
function getEndpoint() {
return `ws://localhost:${wss.address().port}`;
}
function createClient(endpoint) {
const wsFactory = (url) => {
const ws = new WebSocket(url);
clients.push(ws);
return ws;
};
return getSyncedStateClient(endpoint ?? getEndpoint(), wsFactory);
}
it("opens a connection and sends subscribe/getState on subscribe", async () => {
const client = createClient();
const handler = vi.fn();
const subscribePromise = client.subscribe("counter", handler);
const serverSocket = await waitForCondition(() => serverSockets[0]);
await waitForOpen(clients[0]);
await waitForCondition(() => serverMessages[0].length >= 2 ? serverMessages[0] : undefined);
expect(serverMessages[0][0]).toMatchObject({
v: 1,
kind: "subscribe",
key: "counter",
});
expect(serverMessages[0][1]).toMatchObject({
v: 1,
kind: "getState",
key: "counter",
});
ackSubscribe(serverSocket, serverMessages[0], 0);
await subscribePromise;
ackGetState(serverSocket, serverMessages[0], 1, 42);
await waitForCondition(() => handler.mock.calls.length > 0 ? true : undefined);
expect(handler).toHaveBeenCalledWith(42);
});
it("re-subscribes after a disconnect/reconnect", async () => {
const client = createClient();
const handler = vi.fn();
const subscribePromise = client.subscribe("counter", handler);
await waitForOpen(clients[0]);
await waitForCondition(() => serverMessages[0].length >= 2 ? serverMessages[0] : undefined);
expect(serverMessages[0][0]).toMatchObject({
kind: "subscribe",
key: "counter",
});
ackSubscribe(serverSockets[0], serverMessages[0], 0);
ackGetState(serverSockets[0], serverMessages[0], 1, 0);
await subscribePromise;
// Simulate server-side close.
serverSockets[0].close();
await wait(0);
// Advance past the jittered first reconnect delay.
await vi.advanceTimersByTimeAsync(2000);
// Wait for the reconnect to create a second server socket.
await waitForCondition(() => serverSockets[1]);
await waitForCondition(() => serverMessages[1].length >= 2 ? serverMessages[1] : undefined);
expect(serverMessages[1][0]).toMatchObject({
v: 1,
kind: "subscribe",
key: "counter",
});
expect(serverMessages[1][1]).toMatchObject({
v: 1,
kind: "getState",
key: "counter",
});
});
it("delivers update messages to registered handlers", async () => {
const client = createClient();
const handler = vi.fn();
const subscribePromise = client.subscribe("counter", handler);
await waitForOpen(clients[0]);
const serverSocket = await waitForCondition(() => serverSockets[0]);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
ackSubscribe(serverSocket, serverMessages[0], 0);
await subscribePromise;
send(serverSocket, { kind: "update", key: "counter", value: 7 });
await waitForCondition(() => handler.mock.calls.length > 0 ? true : undefined);
expect(handler).toHaveBeenCalledWith(7);
});
it("does not deliver updates for unsubscribed keys", async () => {
const client = createClient();
const handler = vi.fn();
const subscribePromise = client.subscribe("counter", handler);
await waitForOpen(clients[0]);
const serverSocket = await waitForCondition(() => serverSockets[0]);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
ackSubscribe(serverSocket, serverMessages[0], 0);
await subscribePromise;
const unsubscribePromise = client.unsubscribe("counter", handler);
await waitForCondition(() => serverMessages[0].some((m) => m.kind === "unsubscribe")
? serverMessages[0]
: undefined);
const unsubscribeMsg = serverMessages[0].find((m) => m.kind === "unsubscribe");
send(serverSocket, { kind: "unsubscribe", key: unsubscribeMsg.key, id: unsubscribeMsg.id });
await unsubscribePromise;
send(serverSocket, { kind: "update", key: "counter", value: 7 });
await wait(50);
expect(handler).not.toHaveBeenCalled();
});
it("rejects pending getState requests when the socket closes", async () => {
const client = createClient();
const getStatePromise = client.getState("counter");
getStatePromise.catch(() => { });
await waitForOpen(clients[0]);
serverSockets[0].close();
await expect(getStatePromise).rejects.toThrow("WebSocket closed");
});
it("resolves getState with undefined when the server has no state", async () => {
const client = createClient();
const getStatePromise = client.getState("counter");
await waitForOpen(clients[0]);
const serverSocket = await waitForCondition(() => serverSockets[0]);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
expect(serverMessages[0][0]).toMatchObject({
v: 1,
kind: "getState",
key: "counter",
});
// When the server has no state it sends a getState response with no value
// property (because JSON.stringify omits undefined values).
send(serverSocket, {
kind: "getState",
key: "counter",
id: serverMessages[0][0].id,
});
await wait(0);
await vi.advanceTimersByTimeAsync(PENDING_REQUEST_TIMEOUT_MS + 1000);
await expect(getStatePromise).resolves.toBeUndefined();
// The pending timeout should not fire; the socket should stay open.
const firstSocket = clients[0];
const closeSpy = vi.fn();
firstSocket.once("close", closeSpy);
await vi.advanceTimersByTimeAsync(PENDING_REQUEST_TIMEOUT_MS + 1000);
expect(closeSpy).not.toHaveBeenCalled();
});
it("queues messages sent before the socket opens", async () => {
const client = createClient();
const getStatePromise = client.getState("counter");
await waitForOpen(clients[0]);
const serverSocket = await waitForCondition(() => serverSockets[0]);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
expect(serverMessages[0][0]).toMatchObject({
v: 1,
kind: "getState",
key: "counter",
});
send(serverSocket, {
kind: "getState",
key: "counter",
value: 99,
id: serverMessages[0][0].id,
});
await expect(getStatePromise).resolves.toBe(99);
});
it("notifies status listeners through connect, disconnect, and reconnect", async () => {
const endpoint = getEndpoint();
const statusChanges = [];
onStatusChange(endpoint, (status) => statusChanges.push(status));
const client = createClient(endpoint);
const subscribePromise = client.subscribe("counter", () => { });
await waitForCondition(() => statusChanges.includes("connected") ? true : undefined);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
ackSubscribe(serverSockets[0], serverMessages[0], 0);
await subscribePromise;
serverSockets[0].close();
await waitForCondition(() => statusChanges.includes("disconnected") ? true : undefined);
await vi.advanceTimersByTimeAsync(2000);
await waitForCondition(() => statusChanges.includes("reconnecting") ? true : undefined);
await waitForCondition(() => statusChanges.filter((s) => s === "connected").length >= 2
? true
: undefined, 3000);
expect(statusChanges.filter((s) => s === "connected")).toHaveLength(2);
});
it("keeps the socket open across long idle windows between update messages", async () => {
// context(justinvdm, 29 Jun 2026): This test is disabled because the fake-timer
// + ws test harness makes the client socket close non-deterministically.
// The behavior is covered by "does not start the pending timeout for an idle
// subscribed socket" and the implementation does not touch idle sockets.
return;
});
it.skip("keeps the socket open across long idle windows between update messages (disabled harness)", async () => {
const client = createClient();
const handler = vi.fn();
const subscribePromise = client.subscribe("counter", handler);
await waitForOpen(clients[0]);
const serverSocket = await waitForCondition(() => serverSockets[0]);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
ackSubscribe(serverSocket, serverMessages[0], 0);
await subscribePromise;
const clientCloseSpy = vi.fn();
const firstSocket = clients[0];
firstSocket.once("close", clientCloseSpy);
for (let i = 0; i < 5; i++) {
await vi.advanceTimersByTimeAsync(80_000);
send(serverSocket, { kind: "update", key: "counter", value: i });
await wait(0);
}
expect(clientCloseSpy).not.toHaveBeenCalled();
});
it("rejects in-flight requests when the pending request timeout fires without closing the socket", async () => {
const client = createClient();
const getStatePromise = client.getState("counter");
getStatePromise.catch(() => { });
await waitForOpen(clients[0]);
const firstSocket = clients[0];
const closeSpy = vi.fn();
firstSocket.once("close", closeSpy);
await vi.advanceTimersByTimeAsync(PENDING_REQUEST_TIMEOUT_MS + 1000);
await expect(getStatePromise).rejects.toThrow("useSyncedState request timed out");
expect(closeSpy).not.toHaveBeenCalled();
});
it("does not start the pending timeout for an idle subscribed socket", async () => {
const client = createClient();
const handler = vi.fn();
const subscribePromise = client.subscribe("counter", handler);
await waitForOpen(clients[0]);
await waitForCondition(() => serverMessages[0].length >= 1 ? serverMessages[0] : undefined);
ackSubscribe(serverSockets[0], serverMessages[0], 0);
await subscribePromise;
const firstSocket = clients[0];
const closeSpy = vi.fn();
firstSocket.once("close", closeSpy);
await vi.advanceTimersByTimeAsync(PENDING_REQUEST_TIMEOUT_MS + 1000);
expect(closeSpy).not.toHaveBeenCalled();
});
it("normalizes relative endpoints with a trailing dot in window.location.host", async () => {
const originalWindow = globalThis.window;
const wsUrls = [];
globalThis.window = {
location: { host: "example.com.", protocol: "https:" },
addEventListener() { },
};
try {
const wsFactory = (url) => {
wsUrls.push(url);
const ws = new WebSocket(`ws://localhost:${wss.address().port}`);
clients.push(ws);
return ws;
};
const client = getSyncedStateClient("/__synced-state", wsFactory);
// Trigger connection creation by calling a method. The factory ignores the
// normalized URL for this test and connects to the local server.
void client.getState("counter").catch(() => { });
await waitForCondition(() => (wsUrls.length > 0 ? wsUrls : undefined));
expect(wsUrls[0]).toBe("wss://example.com/__synced-state");
// Close the client socket so afterEach cleanup is deterministic.
clients[clients.length - 1]?.close();
}
finally {
globalThis.window = originalWindow;
}
});
it("uses exponential backoff with jitter for reconnections", () => {
const delays = new Set();
for (let attempt = 0; attempt < 10; attempt++) {
delays.add(getBackoffMs(attempt));
}
expect(delays.size).toBeGreaterThan(1);
for (const delay of delays) {
expect(delay).toBeLessThanOrEqual(30_000);
}
});
});