Accessible Component Testing with Jest and jest-axe

Modern web applications strive for inclusivity, ensuring that all users, regardless of their abilities, can interact with digital products effectively. Accessibility testing is crucial for identifying and rectifying issues that might hinder users with disabilities. This challenge focuses on integrating automated accessibility testing into your development workflow using Jest and the jest-axe library to ensure your React components meet accessibility standards.

Problem Description

Your task is to write Jest tests for a given React component that verify its accessibility using jest-axe. You will be provided with a React component and a set of Jest test cases. Your goal is to extend these tests to include accessibility checks, specifically looking for common ARIA (Accessible Rich Internet Applications) violations and other accessibility anti-patterns.

Key Requirements:

• Set up jest-axe within your Jest testing environment.
• Write new test cases that utilize axe from jest-axe to analyze the rendered output of the provided React component.
• Assert that the component passes accessibility checks according to the default axe-core rules.
• Consider how to test components with dynamic ARIA attributes.

Expected Behavior:

Your tests should run successfully and report any accessibility violations found in the rendered component. A passing test indicates that the component, as rendered in the test environment, conforms to the accessibility rules checked by axe-core.

Edge Cases to Consider:

• Components that rely heavily on ARIA attributes (e.g., aria-expanded, aria-hidden, aria-label).
• Components that dynamically change their ARIA attributes based on user interaction or state.
• Components that might have missing or incorrect ARIA attributes.

Examples

Let's consider a simple Button component:

Example 1: Basic Button

React Component (Conceptual):

import React from 'react';

interface ButtonProps {
  label: string;
  onClick: () => void;
}

const Button: React.FC<ButtonProps> = ({ label, onClick }) => {
  return <button onClick={onClick}>{label}</button>;
};

export default Button;

Jest Test (Initial - without jest-axe):

import React from 'react';
import { render, screen, fireEvent } from '@testing-library/react';
import Button from './Button'; // Assuming Button is in Button.tsx

describe('Button', () => {
  test('renders button with correct label', () => {
    render(<Button label="Click Me" onClick={jest.fn()} />);
    const buttonElement = screen.getByText('Click Me');
    expect(buttonElement).toBeInTheDocument();
    expect(buttonElement.tagName).toBe('BUTTON');
  });

  test('calls onClick when clicked', () => {
    const handleClick = jest.fn();
    render(<Button label="Click Me" onClick={handleClick} />);
    const buttonElement = screen.getByText('Click Me');
    fireEvent.click(buttonElement);
    expect(handleClick).toHaveBeenCalledTimes(1);
  });
});

Jest Test (with jest-axe):

You would add a test like this:

import React from 'react';
import { render, screen, fireEvent } from '@testing-library/react';
import { axe, toHaveNoViolations } from 'jest-axe'; // Import axe and matcher
import Button from './Button';

expect.extend(toHaveNoViolations); // Extend Jest with the matcher

describe('Button Accessibility', () => {
  test('passes basic accessibility checks', async () => {
    const { container } = render(<Button label="Click Me" onClick={jest.fn()} />);
    const results = await axe(container); // Run axe on the rendered component
    expect(results).toHaveNoViolations(); // Assert no violations
  });
});

Explanation:

The axe(container) function runs axe-core against the provided DOM node. The toHaveNoViolations() matcher checks the results object returned by axe and asserts that the violations array is empty.

Example 2: Button with aria-label (Potentially problematic)

React Component (Conceptual):

import React from 'react';

interface IconButtonProps {
  icon: React.ReactNode;
  label: string;
  onClick: () => void;
}

const IconButton: React.FC<IconButtonProps> = ({ icon, label, onClick }) => {
  return (
    <button onClick={onClick} aria-label={label}>
      {icon}
    </button>
  );
};

export default IconButton;

Jest Test (with jest-axe):

import React from 'react';
import { render, screen, fireEvent } from '@testing-library/react';
import { axe, toHaveNoViolations } from 'jest-axe';
import IconButton from './IconButton'; // Assuming IconButton is in IconButton.tsx

// Mock an icon component for demonstration
const MockIcon = () => <svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path d="M12 2C6.48 2 2 6.48 2 12s4.52 10 10 10 10-4.52 10-10S17.52 2 12 2zm0 18c-4.41 0-8-3.59-8-8s3.59-8 8-8 8 3.59 8 8-3.59 8-8 8zm-1-13h2v6h-2zm0 8h2v2h-2z" fill="currentColor"/></svg>;

expect.extend(toHaveNoViolations);

describe('IconButton Accessibility', () => {
  test('passes accessibility checks when aria-label is present and descriptive', async () => {
    const { container } = render(<IconButton icon={<MockIcon />} label="Settings" onClick={jest.fn()} />);
    const results = await axe(container);
    expect(results).toHaveNoViolations();
  });

  // This test might fail if aria-label is missing or empty, which `axe-core` would catch.
  // For example, if you rendered `<IconButton icon={<MockIcon />} label="" onClick={jest.fn()} />`
});

Explanation:

This example shows how jest-axe can catch issues like an empty aria-label or a missing aria-label on an element that requires one (e.g., a button with only an icon). axe-core has specific rules to identify these common accessibility pitfalls.

Constraints

• You will be provided with a React component and an existing Jest test file (.spec.tsx).
• Your solution must use TypeScript.
• You should install jest-axe and its peer dependencies (@testing-library/react).
• The tests should be runnable within a standard Jest environment configured for React and TypeScript.
• Focus on implementing the accessibility checks; do not refactor existing functional tests unless strictly necessary for accessibility testing.

Notes

• jest-axe works by integrating axe-core into your Jest tests. It leverages @testing-library/react to render your components into a DOM environment that axe-core can analyze.
• The axe function returns a promise, so your accessibility tests should be marked async and use await.
• The toHaveNoViolations() matcher is provided by jest-axe and is essential for asserting accessibility.
• Familiarize yourself with common ARIA roles and attributes to better understand potential accessibility issues. axe-core has a comprehensive set of rules that cover many of these.
• The provided React component might have varying levels of accessibility. Your task is to test its current state and identify violations. The goal is to add the testing mechanism, not necessarily to fix the component's accessibility issues (though that would be the next step in a real-world scenario).