under-the-hood of test runner: runner.hook.js

Runner.prototype.hook = function (name, fn) {
  // 1. for current suite, get hooks with name x
  var hooks = this.suite.getHooks(name);

  function next(i){
    // 3. grab current hook
    var hook = hooks[i];
    // 4. executed all hooks under name x for suite
    if (!hook) fn()

    // set hooks test context
    hook.ctx.currentTest = ...

    // 5. execute hook.
    hook.run(() => {
      // 6. end of hook trigger next hook
      next(++i)
    });
  }

  // 2. trigger start of hooks
  next(0);
}