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How to check elements are rendered with a specific sorting with react-testing-library?

2 min read 06-10-2024
How to check elements are rendered with a specific sorting with react-testing-library?


Ensuring Your React Components Are Sorted Correctly with react-testing-library

Testing that your React components render elements in the desired order can be crucial for user experience. This article will guide you through using react-testing-library to verify your components render elements with a specific sorting.

The Problem: Verifying Element Order

Imagine you have a list of products, each with a price, and you want to ensure they are displayed in ascending order of price. You might write a test like this:

import { render, screen } from '@testing-library/react';
import ProductList from './ProductList';

const products = [
  { name: 'Product A', price: 10 },
  { name: 'Product B', price: 5 },
  { name: 'Product C', price: 15 },
];

test('ProductList renders products in ascending order of price', () => {
  render(<ProductList products={products} />);
  // ...how to check for sorting here?
});

Using react-testing-library for Order Verification

react-testing-library emphasizes testing from a user perspective. It provides tools to interact with your component like a real user would. We'll use two key functions:

  • screen.getByRole: This function finds an element based on its role (e.g., 'listitem').
  • screen.getAllByRole: This function finds all elements matching the specified role.

Here's an updated test leveraging these functions:

import { render, screen } from '@testing-library/react';
import ProductList from './ProductList';

const products = [
  { name: 'Product A', price: 10 },
  { name: 'Product B', price: 5 },
  { name: 'Product C', price: 15 },
];

test('ProductList renders products in ascending order of price', () => {
  render(<ProductList products={products} />);

  const listItems = screen.getAllByRole('listitem');

  // Assert the first item in the list has the lowest price
  expect(listItems[0]).toHaveTextContent('Product B'); 

  // Assert the last item in the list has the highest price
  expect(listItems[listItems.length - 1]).toHaveTextContent('Product C');
});

Understanding the Approach

This test works by:

  1. Rendering the component: We render the ProductList with our sample products data.
  2. Getting all list items: We use screen.getAllByRole('listitem') to retrieve all the list items rendered by the component.
  3. Checking the text content of the list items: We use toHaveTextContent to ensure the text content of the first and last list item matches the expected products (based on the sorting).

Additional Considerations

  • Complex sorting scenarios: If your sorting involves multiple criteria or complex logic, you might need to iterate through the list items and perform more detailed comparisons.
  • Custom elements: If you use custom elements in your list, adjust the getByRole selector to match the appropriate role or use getByTestId for more specific identification.

Conclusion

react-testing-library provides powerful tools for testing the visual order of elements in your React components. By embracing user-centric testing, you can ensure a consistent and reliable user experience. Remember to adapt your test logic based on the specific sorting requirements of your application.

References:

react-testing-library

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