Mocha before() & beforeEach() execution order with nested describe()

before.js

'use strict';

describe('mocha before hooks', function () {
	before(() => console.log('*** top-level before()'));
	beforeEach(() => console.log('*** top-level beforeEach()'));
	describe('nesting', function () {
		before(() => console.log('*** nested before()'));
		beforeEach(() => console.log('*** nested beforeEach()'));
		it('is a nested spec', () => true);
	});
});

//   mocha before hooks
// *** top-level before()
//     nesting
// *** nested before()
// *** top-level beforeEach()
// *** nested beforeEach()
//       ✓ is a nested spec
//
//
//   1 passing (8ms)

This helped me understand the order in which before() and beforeEach() fire within a nested describe() (or context()).

My initial (wrong) intuition was that the top-level beforeEach() would fire before every nested describe() (and hence before every nested before()), but of course before() / beforeEach() apply to specs (i.e. it()), not scopes.

Is there a way to get a global beforeEach() to run before every nexted before() statement?

top level beforeEach initializes something that is used by the nested before

Thanks @harto, I came here looking for exactly this insight.

Thanks for this! I was having a hard time figuring out what was wrong with my tests.

Is there a way to run a hook before and after each spec?
Eg, there are 3 *.spec.js files
The console should print..

Test started at : 12:00:00
  Spec 1 tests
  ...
  ...
Test Ended at : 12:00:10

Test started at : 12:00:11
  Spec 2  tests
  ...
  ...
Test Ended at : 12:00:15

Test started at : 12:00:15
  Spec 3 tests
  ...
  ...
Test Ended at : 12:00:20

Thanks for this. I was trying to access a nested object property within the nested describe block and getting a TypeError because the beforeEach hook in the top-level describe, where the object was being assigned, was not being called prior to that so the object was in fact undefined.

before

describe('top-level', () => {
  let obj;

  beforeEach(() => {
    obj = {
      nested: {
        property: 'value'
      }
    };
  });

  describe('nested', () => {
    obj.nested.property = 'new-value';
  });
});

after

describe('top-level', () => {
  let obj;

  beforeEach(() => {
    obj = {
      nested: {
        property: 'value'
      }
    };
  });

  describe('nested', () => {
    beforeEach(() => {
      obj.nested.property = 'new-value';
    });
  });
});

this was very helpful!

Thank you!

top level beforeEach initializes something that is used by the nested before

From the example above the nested before() is called before the top level beforeEach().

So if the nested before() relies on the top level beforeEach() to initialize something, the result might be undefined or null