this.addMatchers({
  toBeAbout: function (expected, precision) {
    if (typeof this.actual !== 'number' || typeof expected !== 'number') {
      return false;
    }
    var delta = Math.abs(expected - this.actual);
    precision = precision || 20;
    return delta <= precision;
  },

  toBeNumber: function () {
    return Object.prototype.toString.call(this.actual) === '[object Number]';
  },
  
  toBeHidden: function () {
    return this.actual.classList.contains('hidden');
  },

  toBeVisible: function () {
    return !this.actual.classList.contains('hidden');
  },

  toBeChecked: function () {
    var elem = CLND.dom.closest(this.actual, '[data-role="checkbox"]');
    return this.actual.checked && elem.classList.contains('checkbox_checked');
  },

  toBeUnchecked: function () {
    var elem = CLND.dom.closest(this.actual, '[data-role="checkbox"]');
    return !this.actual.checked && !elem.classList.contains('checkbox_checked');
  }
});