Core htmx client side validation tests

• calls htmx:validation:halted on failure4ms ‣

  var form = make('<form hx-post="/test" hx-trigger="click">' +
          'No Request' +
          '<input id="i1" name="i1" required>' +
          '</form>')
  var errors = null
  var handler = htmx.on(form, 'htmx:validation:halted', function(evt) {
    errors = evt.detail.errors
  })
  try {
    form.click()
    this.server.respond()
  } finally {
    htmx.off(form, handler)
  }
  errors.length.should.equal(1)
  byId('i1').should.equal(errors[0].elt)
  errors[0].validity.valueMissing.should.equal(true)