# fusion-test-utils

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Provides test utility functions for Fusion.js

---

```sh
yarn add fusion-test-utils
```

### Example

```js
import App from 'fusion-core';
import {getSimulator} from 'fusion-test-utils';

// create simulator
const app = new App();
const simulator = getSimulator(app /*, (optional) test plugin with assertions on dependencies */);

// test renders of your application
const ctx = await simulator.render('/test-url', {
  headers: {
    'x-header': 'value',
  }
});
// do assertions on ctx

// test requests to your application
const ctx = await simulator.request('/test-url', {
  headers: {
    'x-header': 'value',
  }
});
// do assertions on ctx
```

---

### API

#### `getSimulator(app: FusionApp, testPlugin?: FusionPlugin) => { request, render, getService }`

Creates a simulator which exposes functionality to simulate requests and renders through your application.
`app` - instance of a FusionApp
`testPlugin` - optional plugin to make assertions on dependencies

#### `getSimulator(...).request(url: String, options: ?Object) => Promise<Context>`

Simulates a request through your application.
`url` - path for request
`options` - optional object containing custom settings for the request
`options.method` - the request method, e.g., GET, POST,
`options.headers` - headers to be added to the request
`options.body` - body for the request

#### `getSimulator(...).render(url: String, options: ?Object) => Promise<Context>`

This is the same as `request`, but defaults the `accept` header to `text/html` which will trigger a render of your application.

#### `getSimulator(...).getService(token: Token<T>) => T`

This is a useful utility for testing the API provided by a plugin. For example:

```js
const app = new App(el, el => el);
app.register(LoggerToken, LoggerPlugin);
const sim = getSimulator(app);
const logger = sim.getService(LoggerToken);
```

#### `createRequestContext(url: String, options: ?Object) => Context`

Creates a mock context object.
`url` - path for request
`options` - optional object containing custom settings for the request
`options.method` - the request method, e.g., GET, POST,
`options.headers` - headers to be added to the request
`options.body` - body for the request


#### `createRenderContext(url: String, options: ?Object) => Context`

The same as `createRequestContext`, but defaults the `accept` header to `text/html` which will trigger a render of the application.

#### `test(testName: String, executor: (assert) => {})`

A block which executes a test case when using [fusion-cli](https://github.com/fusionjs/fusionjs/tree/master/fusion-cli) as a test runner. The first argument is the name of the test, and the second argument is a function that executes your test code. The test case will receive a cross-environment assertion helper with all methods defined in the [assert module](https://nodejs.org/api/assert.html), as well as a `.matchSnapshot()` method.

Example usage:
```js
import React from 'react';
import {test} from 'fusion-test-utils';
import {render} from '@testing-library/react';

import MyComponent from '../my-component';

test('MyComponent snapshot', assert => {
  const {asFragment} = render(<MyComponent />);
  assert.matchSnapshot(asFragment());
  // And optionally, you can pass your own snapshot name as the second argument
  assert.matchSnapshot(asFragment(), 'my snapshot description');
});

test('async functions', async assert => {
  const value = await doSomething();
  assert.equal(true, value, 'something is equal to true');
});
```

#### `mockFunction()`

Returns a mock function which allows you to inspect the mock state via the .mock property.
Example usage:
```js
import {mockFunction, test} from '../index';

test('function mocks', assert => {
  const myMock = mockFunction();
  myMock();
  assert.equal(myMock.mock.calls.length, 1);
});
```