# `@sa11y/assert`

Provides assertAccessible API to check DOM for accessibility issues

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- [Usage](#usage)
  - [Basic Usage](#basic-usage)
  - [Getting Results](#getting-results)
  - [Environment Variables](#environment-variables)

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## Usage

### Basic Usage

```javascript
import { assertAccessible } from '@sa11y/assert';
import { full } from '@sa11y/preset-rules';

// Setup DOM in the state to be tested for accessibility
// ...
// Assert that the current dom has no a11y issues
// Defaults to using
//  - default document context e.g. JSDOM in Jest
//  - base ruleset from @sa11y/preset-rules and
//  - A11yError.checkAndThrow from @sa11y/format
await assertAccessible();

// Can be used to test accessibility of a specific HTML element
const elem = document.getElementById('foo');
await assertAccessible(elem);

// Can be overridden to use custom dom, ruleset or formatter
//  - Specifying null for formatter will result in using JSON stringify
await assertAccessible(document, full, null);
```

### Getting Results

For advanced use cases where you want to get the accessibility results without throwing an error:

```javascript
import { getA11yResultsJSDOM, getViolationsJSDOM, getIncompleteJSDOM } from '@sa11y/assert';
import { extended } from '@sa11y/preset-rules';

// Get both violations and incomplete results
const allResults = await getA11yResultsJSDOM(document, extended, true);

// Get only violations (default behavior)
const violations = await getViolationsJSDOM(document, extended);

// Get only incomplete results
const incomplete = await getIncompleteJSDOM(document, extended);
```

### Environment Variables

-   `SELECTOR_FILTER_KEYWORDS`: Comma-separated list of keywords to filter out violations by CSS selector