could anyone help?)
I've stucked with the problem
function (it) run longer that 500ms

Oh god. It was really painfully. I sat with this problem for several hours(about 4-5).
As a result, the error was that fetch(url) should ALWAYS come immediately followed by ".then()".
You can't write

  let promise = fetch(`...`);
  promise.then(...)
  return promise

But I dont know why. May be it is related with a microtasks stack? If there is anyone who knows, please tell me the topics that I could read

new FetchError(request to ${request.url} failed, reason: ${err.message}, 'system', err)

Ok. Nice exercice for Christmas. I try to write a test for errors. It should throw an error if the given joke id does not exist.

it('should throw an error', async (done) => {
  
  Test.expectError('if no joke found for given id', async () => {
    await sayJoke(url, 12101)
  })
  
  done();
});

This code doesn't work. I think, it get a promise and don't test the method.

How I can implement it ?

You have to add a 'saySetup' and 'sayPunchLine' methods to the object of your result. So that e.g. result.saySetup() returns the corrent answer.

Tests are running against a valid api endpoint (that is hidden from us).
What you have to do :

1. call the Fetch api method using parameter (apiUrl)
2. this function will return the object which has 2 properties. And these properties have function definition (logic to get the jokeounch line...)
3. real api call is hidden from us, so you have to visualize the data using data sample given to us.

A useful link :
https://reactjs.org/docs/higher-order-components.html#use-hocs-for-cross-cutting-concerns

I don't understand what exactly I'm supposed to be returning. I am able to get the result and isolate the correct joke but I don't know what to return nor do I understand the error message I am getting.

The instructions say:

"When you got the joke it should be accessible through a simple API of saySetup and sayPunchLine methods."

Can an example of what a correct return message would look like be posted? I am able to get the return object and find the correct joke but what exactly am I supposed to return?

I have similar questions regarding the error case as well but can't address those till I can solve the above.

What does it mean 'use mock fetch(url)'? Should I mock it myself or use real fetch()?

API URL http://great.jokes/christmas is not reachable.

Old school React class components! Well, that was fun... in a way. Firstly I rewrited everything to functions and hooks, but it turned out the test env does not know what React.useState is. Rewrited everything back again. But enjoyed it nevertheless.

The kata's spec is very confusing: beaming people are supposed to be held in the inTransit properties. But then beaming 3 people should have them all beamed at once? Then what's the purpose of inTransit properties? They are supposed as a temporary storage, which means they shouldn't be tested (not to mention in reality it's not something that's actually needed).

As mentioned below, poor kata design.

The user's already solved the kata.

When you got the joke it should be accessible through a simple API of saySetup and sayPunchLine methods.