2nd Episode: Best practices.

Best practices

During the testing process, our focus is on verifying the desired behaviour rather than specific implementation details.

The Arrange-Act-Assert (AAA) pattern

This widely used pattern helps to ensure that your tests are well-organized and structured correctly. It involves three essential steps: arranging the test environment and setting up any necessary variables, acting by performing the desired action, and asserting that the expected outcome has indeed taken place.
Example:

// Counter.js
import React, { useState } from 'react';

const Counter = () => {
  const [count, setCount] = useState(0);

  const increment = () => setCount(count + 1);

  return (
    <div>
      <h1>Counter: {count}</h1>
      <button onClick={increment}>Increment</button>
    </div>
  );
}

export default Counter;

Test

// Counter.test.jsx
import { fireEvent, render, screen } from '@testing-library/react';
import Counter from './Counter';

test('increments counter when button is clicked', () => {
  // Arrange
  render(<Counter />);
  const button = screen.getByRole('button');

  // Act
  fireEvent.click(button);

  // Assert
  const counterValue = screen.getByText(/1/i);
  expect(counterValue).toBeInTheDocument();
});

While it is valuable to follow industry standards, we should also use our judgment to determine when and how to apply them. It's important to aim for tests that closely resemble the behaviour of the code in a production environment.