Why and What to Test

Why and What to Test

In this lesson — part of Testing Fundamentals — you'll learn why and what to test in Dart and why it matters in real work.

Why it matters

Tests prove your code works and keep it working as you change it.

Key ideas

• What to test
• Arrange-Act-Assert
• Running a test suite
• Good vs. brittle tests

In practice

Here's how it looks in idiomatic Dart:

import 'package:test/test.dart';

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

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

Dart note: The package:test framework is the Dart standard; you group cases with test(...) and assert with expect(actual, matcher).

Try it yourself

Exercise: In Dart, write three tests for a function that reverses a string.

Recap

You now understand why and what to test and can apply it in Dart. Mark this lesson complete and continue to the next one.