under-the-hood of test runner: bdd interface.js

bdd: function bddInterface(suite) {
  var suites = [suite];

  suite.on(Suite.constants.EVENT_FILE_PRE_REQUIRE, function (
    context,
    file,
    mocha
  ) {
    var common = Mocha.interfaces.common(suites, context, mocha);

    context.before = common.before;
    context.after = common.after;
    context.beforeEach = common.beforeEach;
    context.afterEach = common.afterEach;

    context.describe = function (title, fn) {
      return common.suite.create({
        title: title,
        file: file,
        fn: fn,
      });
    };

    context.it = function (title, fn) {
      var suite = suites[0];
      var test = new Test(title, fn);
      test.file = file;
      suite.addTest(test);
      return test;
    };
  });
}