Test pure Dart logic: functions, classes, and business logic. No Flutter framework needed.

// test/math_test.dart
import 'package:test/test.dart';

void main() {
  group('Calculator', () {
    test('adds two numbers', () {
      final calc = Calculator();
      expect(calc.add(2, 3), equals(5));
    });

    test('throws on divide by zero', () {
      final calc = Calculator();
      expect(
        () => calc.divide(1, 0),
        throwsA(isA<ArgumentError>()),
      );
    });
  });
}