Where do I run asynchronous code required for test setup in Jest?

Question

I want to dynamically run multiple tests in Jest inside a for-loop but I am not sure where to place the asynchronous code that my test environment requires.

One option that works is to place all asynchronous code inside a test function and execute an assert statement for each iteration of the for-loop.

 describe('Database Testing', () => {

   test(`Testing ${items}`, async () => {

     const items = await getItems(); //<-- asynchronous code

     for (const item of items) {

        expect('hi').toEqual('hi');
     }
   });
 });

However, if the test fails, I will not be able to pinpoint which loop the assert statement failed in. Instead, I would like a structure similar to below where I dynamically run a test for each iteration of the for-loop.

 describe('Database Testing', () => {

   const items = await getItems(); //<-- asynchronous code

   for (const item of items) {

      test(`Testing ${item}`, async () => {
         expect('hi').toEqual('hi');
       });
    };
 });

I am unable to run the asynchronous code due to the synchronous nature of the describe function. Yet, if I use the async keyword in the describe function, I get the error 'Returning a Promise from "describe" is not supported'.

Where should I run the asynchronous code?

Answer 1

beforeAll can be async. You can also have it functions within describe that are async.

Here is the jest documentation on testing async: https://jestjs.io/docs/en/tutorial-async

beforeAll(async () => {
// do async things
})

describe('whatever', () => {
  it('will do something async', async () => {
    expect.assertions(1);
    // do something async
    //... expect something
  })
})

Just make sure that your expect.assertions matches the appropriate number of assertions .

Answer 2

will something like this work:

 describe('Database Testing', () => {
   getItems().then(items -> {
        for (const item of items) {
           expect('hi').toEqual('hi');
        };
     });
 });