Bootstrap uses [QUnit](http://api.qunitjs.com/), a powerful, easy-to-use JavaScript unit test framework. Each plugin has a file dedicated to its tests in `unit/<plugin-name>.js`.
*`unit/` contains the unit test files for each Bootstrap plugin.
*`vendor/` contains third-party testing-related code (QUnit and jQuery).
*`visual/` contains "visual" tests which are run interactively in real browsers and require manual verification by humans.
To run the unit test suite via [PhantomJS](http://phantomjs.org/), run `grunt test-js`.
To run the unit test suite via a real web browser, open `index.html` in the browser.
## How do I add a new unit test?
1. Locate and open the file dedicated to the plugin which you need to add tests to (`unit/<plugin-name>.js`).
2. Review the [QUnit API Documentation](http://api.qunitjs.com/) and use the existing tests as references for how to structure your new tests.
3. Write the necessary unit test(s) for the new or revised functionality.
4. Run `grunt test-js` to see the results of your newly-added test(s).
**Note:** Your new unit tests should fail before your changes are applied to the plugin, and should pass after your changes are applied to the plugin.
* Each test should have a unique name clearly stating what unit is being tested.
* Each test should test only one unit per test, although one test can include several assertions. Create multiple tests for multiple units of functionality.
* Each test should begin with [`assert.expect`](http://api.qunitjs.com/expect/) to ensure that the expected assertions are run.
* Each test should follow the project's [JavaScript Code Guidelines](https://github.com/twbs/bootstrap/blob/master/CONTRIBUTING.md#js)
### Example tests
```javascript
// Synchronous test
QUnit.test('should describe the unit being tested', function (assert) {
assert.expect(1)
var templateHTML = '<divclass="alert alert-danger fade in">'