Jest run async function ONCE before all tests

Question

I want to use jest for my server unit testing (instead of mocha+chai). Is there a way I can run async function before all tests start (init purposes) only once and not for every

Answer 1

Jest provides beforeAll and afterAll. As with test/it it will wait for a promise to resolve, if the function returns a promise.

beforeAll(() => {
  return new Promise(resolve => {
    // Asynchronous task
    // ...
    resolve();
  });
});

It also supports callback style, if you have some existing test code that uses callbacks, although it's recommended to use promises.

beforeAll(done => {
  // Asynchronous task
  // ...
  done();
});