Why are unit tests needed? Have you ever written them?

Unit tests are needed to verify the correctness of individual parts of the code (functions, methods, classes) in isolation from the rest of the system. They help:

• Quickly identify errors at early stages of development.
• Ensure stability when making changes and refactoring.
• Document the behavior of the code through usage examples.

Yes, I have written unit tests in Flutter projects using the flutter_test package. For example, testing a function that calculates the sum:

import 'package:flutter_test/flutter_test.dart';

int sum(int a, int b) => a + b;

void main() {
  test('sum adds two numbers', () {
    expect(sum(2, 3), 5);
  });
}

Unit tests significantly improve the quality and reliability of the application.