Improve hook pattern of 'this.skip()' in beforeAll hooks

[juergba]

Description

describe('outer suite', function() {
  before(function() {
    console.log('** before-1');
    this.skip();
  });
  before(function() { console.log('** before-2'); });  // second before hook should not run

  it('outer pending test', function() { });

  describe('inner suite', function() {
    before(function(done) {              // inner async before hook should not run
      console.log('**** before: done');
      done();
    });

    it('inner pending test', function() { });

    after(function(done) {               // inner async after hook should not run
      console.log('**** after: done');
      done();
    });    
  });

  after(function() { console.log('** after'); });
});

  outer suite
** before-1
** before-2                  // second before hook should not run
    - outer pending test
    inner suite
**** before: done            // inner async before hook should not run
      - inner pending test
**** after: done             // inner async after hook should not run
** after

  0 passing (16ms)
  2 pending

Description of the Change

• since this.skip() aborts hook execution, subsequent before hooks on the same suite level are not executed anymore.
• inner before/after hooks: explicit async hooks with done argument are not executed anymore.
  Note: sync or promise-returning hooks work correctly, no changes are required.
• test.state: is set to pending.
  We have three state's now: failed, passed, pending

Applicable issues

related #3225

[coveralls]

Coverage increased (+0.02%) to 92.818% when pulling 48bb3be on juergba/pending into 54475eb on master.

[teddibaer]

It seems to me, that the current behavior of mocha regarding calling this.skip inside of before() hooks is not correctly reflected in the documentation, where it states that:

"before/after hooks are skipped unless they are defined at the same level as the hook containing this.skip()"