Testdenken – kleine Assertions, AAA, rot→grün→refaktorisieren

Warum eine Testhaltung?

Eine kleine Assertion

// Minimal assertEqual for quick checks
function assertEqual(actual, expected, name) {
  if (actual === expected) {
    console.log("✅", name);
  } else {
    console.log("❌", name, "expected:", expected, "got:", actual);
  }
}

// Demo check
assertEqual(2 + 3, 5, "adds numbers");

Arrange–Act–Assert

// AAA: Arrange → Act → Assert
// Arrange: prepare inputs
function sum(a, b) { return a + b; }
const a = 2;
const b = 4;

// Act: call the function
const result = sum(a, b);

// Assert: compare
assertEqual(result, 6, "sum returns a + b");

Red→Green→Refactor

// Red → Green → Refactor with a tiny example
// 1) Red: write a failing test (expect wrong implementation)
function greet(name) { return "Hi " + name; } // simple implementation

// Intentionally failing expectation first (red)
assertEqual(greet("Ayla"), "Hello Ayla", "greet says Hello"); // likely fails

// 2) Green: fix the code to satisfy the test
function greetFixed(name) { return "Hello " + name; }
assertEqual(greetFixed("Ayla"), "Hello Ayla", "greet says Hello (fixed)");

// 3) Refactor: improve code without changing behavior
function greetRefined(name) {
  const cleaned = String(name).trim();
  return "Hello " + cleaned;
}
assertEqual(greetRefined(" Ayla "), "Hello Ayla", "greet trims input");

Verhaltensorientierte Namen

// Clear names describe behavior, not internals
function isAdult(age) { return age >= 18; }

assertEqual(isAdult(18), true, "isAdult returns true at boundary 18");
assertEqual(isAdult(17), false, "isAdult returns false below boundary");

Kleine, fokussierte Tests

Quiz zum AAA-Muster

Zusammenfassung