code: public OverviewStats add(OverviewStats other) {
          this.addFeaturesFailed(other.getFeaturesFailed());
          this.addFeaturesKnown(other.getFeaturesKnown());
          this.addFeaturesPassed(other.getFeaturesPassed());
          this.addFeaturesUndefined(other.getFeaturesUndefined());
          this.addScenariosFailed(other.getScenariosFailed());
          this.addScenariosKnown(other.getScenariosKnown());
          this.addScenariosPassed(other.getScenariosPassed());
          this.addScenariosUndefined(other.getScenariosUndefined());
          this.addStepsFailed(other.getStepsFailed());
          this.addStepsKnown(other.getStepsKnown());
          this.addStepsPassed(other.getStepsPassed());
          this.addStepsUndefined(other.getStepsUndefined());
          return this;
      }
docs: Merges 2 overview statistic structures where all corresponding values are
  simply added to current object.
  @param other the other structure of the {@link OverviewStats} type to add values from.
  @return the structure containing the sum of current statistics and the statistics from the parameter.