Two describe blocks execute despite .only

[bahmutov]

In branch https://github.com/bahmutov/effective-e2e-testing-with-cypress/tree/double-only

when I have in cypress/integration/todo-spec.js two describe blocks with one having .only both run.

describe.only('main features', function () {
  it('first spec', function () {})
})

describe('main features with assertions', function () {
  it('second spec', function () {})
})

The above should execute only "main features" but Cypress 0.20.0 has

Here is the code bundled

(function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
'use strict';

describe.only('main features', function () {
  it('first spec', function () {});
});

describe('main features with assertions', function () {
  it('second spec', function () {});
});

},{}]},{},[1]);

Notice that the first describe title is a substring of the second. If I change the first one, it will run correctly by itself

describe.only('main 2 features', function () {
  it('first spec', function () {})
})

describe('main features with assertions', function () {
  it('second spec', function () {})
})

and if I change second describe title it will run again two describe blocks

describe.only('main 2 features', function () {
  it('first spec', function () {})
})

describe('main 2 features with assertions', function () {
  it('second spec', function () {})
})

[bahmutov]

Probably Mocha 2.x issue, fixed in Mocha 3.x