Testing Basics: Unit Tests & TDD

// Functions to test
function add(a, b) {
  return a + b;
}

function isPrime(n) {
  if (n <= 1) return false;
  for (let i = 2; i <= Math.sqrt(n); i++) {
    if (n % i === 0) return false;
  }
  return true;
}

function formatCurrency(amount, currency = "INR") {
  if (typeof amount !== "number") throw new TypeError("Amount must be a number");
  if (amount < 0) throw new RangeError("Amount cannot be negative");
  return currency === "INR" ? `₹${amount.toFixed(2)}` : `$${amount.toFixed(2)}`;
}

// Unit tests (Jest/Vitest syntax)
// describe("add", () => {
//   test("adds two positive numbers", () => {
//     expect(add(2, 3)).toBe(5);
//   });
//   test("handles negative numbers", () => {
//     expect(add(-1, 1)).toBe(0);
//   });
//   test("handles zero", () => {
//     expect(add(0, 0)).toBe(0);
//   });
// });

// describe("isPrime", () => {
//   test("returns false for 0 and 1", () => {
//     expect(isPrime(0)).toBe(false);
//     expect(isPrime(1)).toBe(false);
//   });
//   test("identifies prime numbers", () => {
//     expect(isPrime(2)).toBe(true);
//     expect(isPrime(7)).toBe(true);
//     expect(isPrime(13)).toBe(true);
//   });
//   test("identifies non-prime numbers", () => {
//     expect(isPrime(4)).toBe(false);
//     expect(isPrime(9)).toBe(false);
//   });
// });

// Manual testing simulation
console.log("Testing add:");
console.assert(add(2, 3) === 5, "2 + 3 should equal 5");
console.assert(add(-1, 1) === 0, "-1 + 1 should equal 0");
console.log("✅ add tests passed");

console.log("\nTesting isPrime:");
console.assert(isPrime(7) === true, "7 should be prime");
console.assert(isPrime(4) === false, "4 should not be prime");
console.log("✅ isPrime tests passed");