Jest: is it possible to loop its in Jest

[golfapipol]

Do you want to request a _feature_ or report a _bug_?
feature

What is the expected behavior?
is it possible to loop its in Jest

describe('...', () => {
    // first way
    for (let test in tests) {
        it('...', () => {
            expect(...).toBe(...)
        })
    }
    // second way
    tests.forEach((test) => {
        it('...', () => {
            expect(...).toBe(...)
        })
    })
})

[cpojer]

yes it is, just do it like you wrote.

[golfapipol]

but I got this error: JavaScript heap out of memory

const testcases = require('./testcases.data') // it's JSON
describe('...', () => {
    testcases.forEach((test) => {
         it('...', () => {
             expect(...).toBe(...)
         })
    })
})

[cpojer]

that means it is very likely you have an infinite loop somewhere and node just crashes.

[golfapipol]

Thank @cpojer maybe I do thing wrong

[pedro-mass]

You don't get the before/after hooks making tests dynamically for some reason. I'm guessing the dynamic functions are out of scope.

[nazreen]

@cpojer is it also doable with forEach? I'm encountering a race to the finish situation

I have a beforeAll() that fetches info from a local API endpoint.

the it() inside my forEach seems to sometimes run before the done() is called in the beforeAll()

[faceyspacey]

What you can't do unfortunately is create tests dynamically where you have to do some async setup work, eg:

const createTest = async (config) => {
   const foo = await api(config.url)

   for (let test in config.tests) {
        it('...', () => {
            expect(...).toBe(...)
        })
    }
}

createTest(config)

That would work if there was no async/await.

[ghost]

I am running into the same problem with Puppeteer and Jest.

[MiguelMadero]

I just ran into this same issue. My setup needs to be async, but I guess jest needs to discover all the it blocks ahead of time

[deftomat]

The same here, we need to call beforeAll to upload a files to S3 bucket. However, a dynamically created it(...) is called before result from beforeAll resolves.

[SimenB]

All describes, its and tests must be defined synchronously. Doing async work in hooks is possible though, and to use that inside tests. You cannot use it to _define_ tests, though.

[A-Atrash]

Neither for loop nor forEach are working. Jest is not able to see any test!

fs.readdir('./testingImages/', async (err, images) => {
    if (err) {
      throw err;
    }
    for (const image in images) {
      if (image) {
        const imagePath = './testingImages/' + image;
        it(`convertor should validate the image ${image}`, async () => {
          const convert: any = await imageConvertor(imagePath);
          expect(typeof convert).toBe('string');
          fs.unlinkSync(convert); // clean up
        });
      }
    }
  });

Jest error:

Your test suite must contain at least one test.

[thymikee]

@A-Atrash see: https://jestjs.io/docs/en/troubleshooting#defining-tests

[A-Atrash]

@thymikee OK, so there is no way then?

[thymikee]

There's always a way! You have at least 2 options:
1) generate tests based on the testingImages/ using a script.
2) put everything in one test statement

I lean towards 1) because it will result in better test parallelization, while solution 2) will always run tests one-by-one

[A-Atrash]

@thymikee can you give me a small example of the first 😁

[thymikee]

No time for that. I'm sure you'll figure it out :)

[SimenB]

You can use fs.readdirSync as well, that should be possible

[A-Atrash]

@thymikee I did it 😈
@SimenB Thanks!

[Relequestual]

@A-Atrash Care to share your solution to dynamically creating tests?

[sbuckpesch]

Dirty hack:

Run your tests via runCLI. Before the call you can do you async requests and wait for it. Then you pass in a static data to you Jest config as global:

test.ts

import {runCLI} from 'jest';
import projectConfig from '../../../jest.config.js';

export const test = async (specs: string) => {
        // Do your async preparation
        const requests = await dereference(specs);
        // Run jest
        const result = await runCLI({
            ...projectConfig,
            globals: JSON.stringify({requests}) // <--- Here we pass it in
        }, [join(__dirname, '../project/root/')]);
}

mydynamic.test.ts

// Write your test
describe(`Test endpoints of ${specsPath}`, () => {
    // @ts-ignore
    const requests = global.requests; // <--- Here you go. Your async data
    for (const request of requests) {
        it(`${request.method} ${request.path}`, async () => {
             // Yeah, now you can access even everything initialized in beforeAll() :-)
        });
    }
});