assert-exercises.md

Unit testing exercises

For each of these problems, write the unit test first, then write the function. Make sure that it passes the test.

Convert km to m. For example, write a function that converts kilometers to meters, as well as a function that tests this code. There are 1,000 meters in 1 kilometer. The code might look like this:

function kmToM (km) {
  let m = km / 1000;
  return m;
}


function test_kmToM() {
  assert(kmToM(1) === 1000, "1km should = 1000m");
  assert(kmToM(52) === 52000, "52km should = 52000m");
  assert(kmToM(.05) === 50, ".05km should = 50m");
  assert(kmToM(-3) === -3000, "-3 should = -3000m");
  assert(kmToM(0) === 0, "0 should = 0");
}

1. Tbs to cups. There are 16 tablespoons in a cup. Write a function that converts Tbs to cups. It should take the number of tablespoons as an argument and return the number of cups.

2. Kilos (kg) to pounds (lbs). Write a function that converts kilograms to pounds. Use the conversion rate of 2.2 pounds for each kilogram.

3. Weight of water. 1 liter of water weighs exactly 1 kilogram. Write a function that has a parameter for the volume of water in liters returns the weight of water in pounds, something like this: function litersOfWaterInLbs(liters)

4. Format currency. Write a function fmtCurrency(amount, symbol) that takes a currency amount as a real number and returns a string, with the currency symbol at the start followed by the amount rounded to 2 decimal places (using toFixed).

5. Making pizza. You make pizzas. When you make the sauce, if you only use 1 can of tomatoes, it's not enough for the whole pie. You need 1.5 cans per pizza. When you are making a lot of pizzas (and a big pot of sauce), you want a function that tells you how many cans of tomatoes to buy. Of course, you can't buy half a can of tomatoes, so you must round up if there's a half can. To "round up", use Javascript's built in Math.round function.

Rounding numbers (optional challenge)

Javascript's built-in Math.round(n) rounds any real number to the closest integer. Write a more flexible function, round(n, p) that rounds a number n to the number of decimal places specified by p.

Examples:

⠕ round(2.457, 2);
=> 2.46
⠕ round(3.98746144, 4)
=> 3.9875
⠕ round(3.98746144, 0)
=> 4
⠕ round(52, -1)
=> 50
⠕ round(55, -1)
=> 60
⠕ round(542, -2)
=> 540

Your tests should test all of these examples.