# Enforce assertion to be made in a test body (`expect-expect`)

Ensure that there is at least one `expect` call made in a test.

## Rule details

This rule triggers when there is no call made to `expect` in a test, to prevent
users from forgetting to add assertions.

Examples of **incorrect** code for this rule:

```js
it('should be a test', () => {
  console.log('no assertion');
});
test('should assert something', () => {});
```

Examples of **correct** code for this rule:

```js
it('should be a test', () => {
  expect(true).toBeDefined();
});
it('should work with callbacks/async', () => {
  somePromise().then(res => expect(res).toBe('passed'));
});
```

## Options

```json
{
  "jest/expect-expect": [
    "error",
    {
      "assertFunctionNames": ["expect"]
    }
  ]
}
```

### `assertFunctionNames`

This array option specifies the names of functions that should be considered to
be asserting functions. Function names can use wildcards i.e `request.*.expect`,
`request.**.expect`, `request.*.expect*`

Examples of **incorrect** code for the `{ "assertFunctionNames": ["expect"] }`
option:

```js
/* eslint jest/expect-expect: ["error", { "assertFunctionNames": ["expect"] }] */

import { expectSaga } from 'redux-saga-test-plan';
import { addSaga } from '../src/sagas';

test('returns sum', () => {
  expectSaga(addSaga, 1, 1)
    .returns(2)
    .run();
});
```

Examples of **correct** code for the
`{ "assertFunctionNames": ["expect", "expectSaga"] }` option:

```js
/* eslint jest/expect-expect: ["error", { "assertFunctionNames": ["expect", "expectSaga"] }] */

import { expectSaga } from 'redux-saga-test-plan';
import { addSaga } from '../src/sagas';

test('returns sum', () => {
  expectSaga(addSaga, 1, 1)
    .returns(2)
    .run();
});
```

Since the string is compiled into aa regular expression, you'll need to escape
special characters such as `$` with a double backslash:

```js
/* eslint jest/expect-expect: ["error", { "assertFunctionNames": ["expect\\$"] }] */

it('is money-like', () => {
  expect$(1.0);
});
```

Examples of **correct** code for working with the HTTP assertions library
[SuperTest](https://www.npmjs.com/package/supertest) with the
`{ "assertFunctionNames": ["expect", "request.*.expect"] }` option:

```js
/* eslint jest/expect-expect: ["error", { "assertFunctionNames": ["expect", "request.*.expect"] }] */
const request = require('supertest');
const express = require('express');

const app = express();

describe('GET /user', function() {
  it('responds with json', function(done) {
    request(app)
      .get('/user')
      .expect('Content-Type', /json/)
      .expect(200, done);
  });
});
```
