Jest Accessibility Testing: Simulating Screen Reader Behavior

This challenge focuses on creating robust accessibility tests for web applications using Jest and a popular accessibility testing library. Understanding how screen readers interpret and announce UI elements is crucial for building inclusive applications. This exercise will help you simulate common screen reader interactions and verify that your components are accessible.

Problem Description

Your task is to write Jest tests that verify the accessibility of a given HTML component, specifically simulating how a screen reader would interact with it. You'll use a library like jest-axe to perform these checks. The tests should identify common accessibility issues such as missing alt text for images, improper ARIA attribute usage, and elements that are not focusable.

Key Requirements:

1. Setup Jest with jest-axe: Configure your Jest environment to use jest-axe for accessibility assertions.
2. Test a Sample Component: Create a sample HTML component (or use an existing one) that represents a common UI pattern (e.g., a button with an icon, a form with input fields, an image gallery).
3. Write Accessibility Tests: Implement Jest tests that run jest-axe against your sample component's rendered output.
4. Assert for Accessibility Violations: Assert that the component passes or fails specific accessibility rules based on predefined criteria.
5. Handle Different Scenarios: Write tests for both accessible and intentionally inaccessible versions of your component to demonstrate your understanding.

Expected Behavior:

• Tests for an accessible component should pass (i.e., jest-axe should report no violations or only expected minor violations).
• Tests for an inaccessible component should fail, clearly indicating the accessibility issues found by jest-axe.
• Your tests should be clear, readable, and demonstrate an understanding of common accessibility pitfalls.

Important Edge Cases:

• Dynamic Content: Consider how accessibility might be affected by dynamically added or removed content.
• Complex Interactive Elements: Test components with more intricate interactions, like dropdowns or modal dialogs.
• Custom Elements: If using custom HTML elements, ensure they are appropriately role-defined.

Examples

Example 1: Accessible Button

• Input (Conceptual HTML):

  <button aria-label="Close modal">
    <svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
      <path d="M18 6L6 18" stroke="black" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
      <path d="M6 6L18 18" stroke="black" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/>
    </svg>
  </button>
  

• Output (Conceptual Jest Assertion):

  import { render } from '@testing-library/react'; // Assuming React for rendering
  import { axe, toHaveNoViolations } from 'jest-axe';
  import MyAccessibleButton from './MyAccessibleButton'; // Your component
  
  expect.extend(toHaveNoViolations);
  
  it('should be accessible', async () => {
    const { container } = render(<MyAccessibleButton />);
    await expect(axe(container)).toHaveNoViolations();
  });
  

• Explanation: The button has an aria-label that describes its purpose, making it understandable to screen readers even though it only contains an icon. The jest-axe check should pass.

Example 2: Inaccessible Image

• Input (Conceptual HTML):

  <img src="logo.png" />
  

• Output (Conceptual Jest Assertion):

  import { render } from '@testing-library/react';
  import { axe, toHaveNoViolations } from 'jest-axe';
  import MyInaccessibleImage from './MyInaccessibleImage'; // Your component
  
  expect.extend(toHaveNoViolations);
  
  it('should have alt text', async () => {
    const { container } = render(<MyInaccessibleImage />);
    const results = await axe(container);
    expect(results.violations.length).toBeGreaterThan(0);
    expect(results.violations.some(v => v.id === 'image-alt')).toBe(true);
  });
  

• Explanation: The <img> tag is missing the alt attribute, which is crucial for screen readers to describe the image's content. jest-axe will detect this violation, and the test should assert that violations exist, specifically an image-alt violation.

Example 3: Form with Missing Labels

• Input (Conceptual HTML):

  <div>
    <input type="text" id="username" />
    <input type="password" id="password" />
    <button type="submit">Login</button>
  </div>
  

• Output (Conceptual Jest Assertion):

  import { render } from '@testing-library/react';
  import { axe, toHaveNoViolations } from 'jest-axe';
  import MyInaccessibleForm from './MyInaccessibleForm';
  
  expect.extend(toHaveNoViolations);
  
  it('should have associated labels', async () => {
    const { container } = render(<MyInaccessibleForm />);
    const results = await axe(container);
    expect(results.violations.length).toBeGreaterThan(0);
    expect(results.violations.some(v => v.id === 'label')).toBe(true);
  });
  

• Explanation: The input fields lack associated <label> elements, making it difficult for screen readers to convey their purpose. jest-axe will flag this as a missing label violation.

Constraints

• Testing Framework: You must use Jest as your testing framework.
• Accessibility Library: You must use jest-axe (or a comparable, widely-used accessibility testing library integrated with Jest).
• Language: All test files and any supporting code must be written in TypeScript.
• Rendering: You'll need a way to render your HTML components into a DOM-like structure that jest-axe can analyze. Libraries like @testing-library/react, @testing-library/vue, or a simple DOM emulator can be used.
• Component Scope: Focus on testing individual components or small, isolated pieces of UI.

Notes

• Familiarize yourself with the common accessibility rules provided by jest-axe (e.g., image-alt, label, aria-roles, tabindex).
• Consider how aria-label, aria-labelledby, aria-describedby, and semantic HTML elements contribute to accessibility.
• When writing tests, aim to be descriptive about what accessibility aspect you are testing.
• You may need to install additional dependencies like @testing-library/jest-dom for better DOM assertions.