Jasmine Async Test Generation

let's imagine we have a promise that does a large amounts of operations and return helper functions. A banal example: const testPromise = testFn => () => { const helper =

Solution 1:

Take a look at Defining Tests. The doc says:

Tests must be defined synchronously for Jest to be able to collect your tests.

This is the principle for defining test cases. Which means the it function should be defined synchronously. That's why your second example doesn't work.

Some I/O operations should be done in beforeAll, afterAll, beforeEach, afterEach methods to prepare your test doubles and fixtures. The test should be isolated from the external environment as much as possible.

If you must do this, maybe you can write the dynamically obtained testHelper function to a static js file, and then test it in a synchronous way

Solution 2:

As it was noted, describe serves to group tests.

This can be achieved with beforeAll. Since beforeAll should be called any way, it can be moved to testPromise:

constprepareHelpers = (testFn) => {
  beforeAll(() => {
    ...
    return helper.then(testFn);
  })
}

describe('Async describe approach', () => {
  let testHelper;

  prepareHelpers(helpers => { testHelper = helpers.testHelper });
  ...