URL: /code/apps/analytics-and-experiments/test · Id: `page:/code/apps/analytics-and-experiments/test`

# Hypothesis.test

> Ties a Hypothesis to the Experiment that decides it, and marks it testing.

POST https://api.sb/{your-domain}/hypotheses/{hypothesis}/test

Ties a [Hypothesis](https://startupbuilder.dev/business/nouns/hypothesis) to the [Experiment](https://startupbuilder.dev/business/nouns/experiment) that decides it, and marks it testing.

- **Action class:** None
- **Approval:** Runs on its own
- **Emits:** `Hypothesis.tested`
- **Price:** Free

```text title="Run it · Ask"
Test “a question subject lifts replies” with the subject-line experiment.
```

```ts title="Run it · SDK"
import { $ } from 'startup-builder'

const result = await $.try.Hypothesis.test({ hypothesis: 'https://api.sb/leaseline.app/hypotheses/hypothesis_Qs1hY5pT8e', experiment: 'https://api.sb/leaseline.app/experiments/experiment_Wb6nC1vZ8q' })
```

```json title="Run it · Response"
{
  "api": "https://api.sb/leaseline.app",
  "hypothesis": {
    "$id": "https://api.sb/leaseline.app/hypotheses/hypothesis_Qs1hY5pT8e",
    "$type": "Hypothesis",
    "status": "testing"
  },
  "action": {
    "operation": "Hypothesis.test",
    "mode": "try",
    "status": "done"
  }
}
```

Its Inputs, Outputs, Effects and guards quote [the hub’s `Hypothesis.test`](https://startupbuilder.dev/business/nouns/hypothesis/test); this page adds what each Venue honors, its limits and a worked call. It is one of the [Verbs](https://startupbuilder.dev/business/nouns/verb) of [Analytics and experiments](/code/apps/analytics-and-experiments#verbs).

## Inputs
| Name | Type | Default | Meaning |
| --- | --- | --- | --- |
| `hypothesis` | `Hypothesis` | Required | The Hypothesis to test. |
| `experiment` | `Experiment` | Required | The Experiment that decides it. |

## Outputs
| Field | Type | What `null` means |
| --- | --- | --- |
| `hypothesis` | `Hypothesis` | Never null: the Hypothesis, now testing. |

## Effects
**Action class**

None: no approval rule names it, so it runs within its seat’s Permissions and Limits

**Modes**

- `try`: Runs every check and returns the record as it would be; nothing is stored.
- `send`: Returns a pending Action at once; `Hypothesis.tested` fires when it is done.
- `do`: Waits for the Action to finish and returns the record.

**Idempotency**

Only with a key: the same `Idempotency-Key` and input return the first Action, and the same key with other input returns `409`.

**Saved or shared**

The Hypothesis is saved as the call leaves it, with the Action that changed it.

**Emits**

`Hypothesis.tested` with `{ hypothesis }`

**Performed by**

Whichever seat calls it

**Price**

Free on your own account: the platform charges nothing for the call.

## On each Venue
It acts on your own records and reaches no Venue, so every account answers the same way.

## What try does
Runs every check the call meets and returns the record as it would be; nothing is stored, sent or posted.

## Refuses when
The hub sets no guard of its own on this call: it refuses only on the shared checks every write meets (a missing record, a Permission the seat lacks).

## When it waits
Returns in one response; nothing waits.

## Example
In `send` mode the call returns its pending Action at once, and `Hypothesis.tested` delivers the result.

**Ask**

```text
Test “a question subject lifts replies” with the subject-line
experiment.
```

**API**

```bash
curl -X POST "https://api.sb/leaseline.app/hypotheses/hypothesis_Qs1hY5pT8e/test?mode=send" \
  -H "Authorization: Bearer $SB_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "experiment": "https://api.sb/leaseline.app/experiments/experiment_Wb6nC1vZ8q"
}'
```

**CLI**

```bash
npx startup-builder do Hypothesis.test --send --data '{
  "experiment": "https://api.sb/leaseline.app/experiments/experiment_Wb6nC1vZ8q"
}'
```

`--send` returns the pending Action at once.

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "mode": "send",
    "code": "return await $.Hypothesis.test({ experiment: 'https://api.sb/leaseline.app/experiments/experiment_Wb6nC1vZ8q' })"
  }
}
```

**SDK**

```ts
import { $ } from 'startup-builder'

const result = await $.send.Hypothesis.test({
  hypothesis: 'https://api.sb/leaseline.app/hypotheses/hypothesis_Qs1hY5pT8e',
  experiment: 'https://api.sb/leaseline.app/experiments/experiment_Wb6nC1vZ8q',
})
```


```json title="Response, in send mode"
{
  "mode": "send",
  "action": {
    "$id": "https://api.sb/leaseline.app/actions/action_Sd3kQ9vT2w",
    "operation": "Hypothesis.test",
    "status": "pending",
    "reason": "running"
  }
}
```

To retry, send the same `Idempotency-Key`: the retry returns the first answer for $0. A new key reads again.

## Used by
None.

## Related
[`Metric.query`](/code/apps/analytics-and-experiments/query) · [`Metric.watch`](/code/apps/analytics-and-experiments/watch) · [`Experiment.start`](/code/apps/analytics-and-experiments/start) · [`Experiment.conclude`](/code/apps/analytics-and-experiments/conclude) · [`Dashboard.ask`](/code/apps/analytics-and-experiments/ask) · [`Metric.define`](/code/apps/analytics-and-experiments/define) · [`Event.capture`](/code/apps/analytics-and-experiments/capture) · [`Dashboard.schedule`](/code/apps/analytics-and-experiments/schedule)