# Testing (/docs/hooks/testing)

Hooks has no simulator. Messages sent with a sandbox (`coss_test_…`) key are delivered for real, so
your test endpoint gets the same signed request, retries and attempts as a live one. What's
different:

- **Nothing is billed**, however many messages you send.
- **The limits are lower**: 100 applications, 5 endpoints per application and 2,000 deliveries a day
  per environment ([limits](/docs/hooks/delivery#limits)).
- **The portal can be embedded from `http://localhost`** while you develop.
- **Failing endpoints don't count against your [reputation](/docs/reputation).**

## The whole loop [#the-whole-loop]

Endpoints must be public `https://` URLs, so use a tunnel or a request inspector to reach your
machine: `localhost` and private addresses are refused. `coss listen` doesn't help here, since it
forwards the environment's own [webhooks](/docs/webhooks), not Hooks deliveries.

```sh
coss hooks event-types create invoice.paid --example '{"invoice_id":"in_1","amount":4200}'
coss hooks apps create "Test customer" --uid test-customer
coss hooks endpoints add test-customer --url https://your-tunnel.example/hooks
coss hooks send test-customer invoice.paid
coss hooks deliveries test-customer
coss hooks attempts test-customer <delivery>
```

`coss hooks endpoints add` prints the endpoint's signing secret: give it to your receiver to
[verify requests](/docs/hooks/receiving#verify-every-request). `coss hooks attempts` shows what each
request got back, and `coss hooks portal test-customer --open` shows your customer's view of it all.

To try one endpoint without reaching the application's others, send it a test message, which is
free in live environments too:

```ts twoslash
import { Coss } from "coss";
// A sandbox key: coss_test_…
const coss = new Coss();
declare const endpointId: string;
// ---cut---
const { data: message } = await coss.hooks.endpoints.sendTest("test-customer", endpointId, {
  event_type: "invoice.paid",
});
// Without a `payload`, it uses the event type's first example.
```

## Failures [#failures]

Point an endpoint at a URL that answers `500` to watch the real [retry
schedule](/docs/hooks/delivery#retries). `coss hooks deliveries test-customer --status failed` lists
what gave up, and `coss hooks retry test-customer <delivery>` tries one again.

Waiting 5 days for an endpoint to be disabled isn't practical, so test your handler for that event
with a sample, which goes to your own [webhook endpoints](/docs/webhooks) and `coss listen`:

```sh
coss trigger hook_endpoint.disabled
```