Adding our first test

Let's create a new file within the top level directory called add.js. It will be a function that takes two numbers, and returns the added value:

function add(x, y) {
  return x + y;
}

module.exports = add;

And let's add the subsequent test:

var add = require("./add");

describe("add", function () {
  it("adds 2 + 3 to be 5", function () {
    expect(add(2, 3)).toBe(5);
  });
});

We can re-run the tests and see that things are looking better:

Your Turn

We now want a multiply function, with the relevant tests. Create the your new JavaScript file for multiplying, and create a test - remember that the test file extension should be .spec.js

Remember to run your tests with yarn run test

multiply.js

function multiply(x, y) {
  return x * y;
}

module.exports = multiply;

multiply.spec.js

var multiply = require("./multiply");

describe("multiply", function () {
  it("multiplies 2 * 3 to be 6", function () {
    expect(multiply(2, 3)).toBe(6);
  });
});