Jest Katas

These katas will give you some hands-on experience in writing tests in Jest. To run your tests, run yarn test in your terminal. To run a specific test in isolation, run yarn test -t 'yourTestNameHere'.

Use this list of Jest expect matchers to help you write your tests.

1. TDD: fizzBuzz

Your task is to write a function, fizzBuzz, that accepts a number and returns a string:

• 'fizz' if the number is divisible by 3;
• 'buzz' if the number is divisible by 5;
• 'fizzbuzz' if the number is divisible by both 3 and 5.
• '{number}' if the number doesn't fulfil any of the above conditions.

As you create the function in fizzbuzz.js, you should also write tests in index.test.js. You'll need to create your own test cases as you go.

Edge cases to consider:

• what should fizzbuzz(0) return?
• what should happen if the function is passed a string?

2. Mocking functions: mapWithCb

The mapwithCb function accepts an array and a callback. It maps over the array with the callback, so we can expect the callback function to be called multiple times.

Your task is to write tests for mapWithCb, which will involve writing a mock function (aka a spy) for the callback function. The test cases have been provided for you.

3. Mocking network responses with nock: getPokemon

The getPokemon function uses the isomorphic-fetch library to get data from PokeAPI. It returns a JSON object.

Your task is to write tests for getPokemon, using the nock library to mock network responses. You'll need to create your own test cases.

Things to consider:

• What sort of data does PokeAPI return? Use the 'Try it now' section on the website to inform your mocked data.
• Async functions don't throw errors in the same way as normal functions. getPokemon() and getPokemon('cartman') will behave differently.