Custom checkbox validation on submit
How can I configure Vee Validator so that it evaluates the oneChecked validator with the call of this.$validator.validateAll();?


Yes, you can use validateAll(), you're just not passing the fields for it to validate. Here's an example on how to do this:

methods: {
  validateBeforeSubmit(e) {
    this.$validator.validateAll({
      name0: true
    });
    console.log('validator', this.errors);
    if (!this.errors.any()) {
      alert('succesfully submitted!');
    }
  }
}


Taken from here.


  Is it possible to pass the this.options array into validate method of oneChecked validator? (Would be more re-usable. I've tried passing as array with JSON.stringify but couldn't get it to work.)


Why pass it as a parameter when it's already a constant?

Consider this:

created() {
  this.$validator.extend('oneChecked', {
    getMessage: field =&gt; 'At least one ' + field + ' needs to be checked.',
    validate: (value, [testProp]) =&gt; {
      return value || Checkboxes.data().options.some((option) =&gt; option[testProp]);
    }
  });
},


This also provides you some protection for when data().options inevitably has more than 3 elements in it.