How do I test (jest) to expect return?

Question

Using Jest how do I test for return

For example using Lambda:

exports.handler = async (event, context, callback) => {
  try {
    const orders = await getOrders();

    if (!orders) {
      console.log("There is no Orders");
      return; //<< How do test this?
    }

    // Something else
  } catch (err) {
    throw new;
  }
};

I am able to test the console log but I also like to test to expect return as well

Currently I am using this in the test:

  it("should terminate if there is no order", async () => {
    console.log = jest.fn();

    let order = await func.handler();
     expect(console.log.mock.calls[0][0]).toBe('There is no Orders');
  });

Answer 1

Function with no return will return 'undefined' so you can test for that using not.toBeUndefined();

Answer 2

Simply expect the value to be undefined:

expect(order).toBeUndefined();

Answer 3

Necroposting here, but jest now has toReturn and toReturnWith, without and with arguments assessing, accordingly. And also there are toHaveReturned and toHaveReturnedWith to fit new language.

You can use it on spyOn'ed variant of your handler:

it("should terminate if there is no order", async () => {
  jest.spyOn(func, "handler")
  console.log = jest.fn();

  let order = await func.handler();
  expect(func.handler).toHaveReturned();
});