new_contents: from django.test import TestCase
  
  from go.apps.jsbox.forms import JsboxForm
  
  
  class JsboxFormTestCase(TestCase):
      def test_to_metdata(self):
          form = JsboxForm(data={
              'javascript': 'x = 1;',
          })
          self.assertTrue(form.is_valid())
          metadata = form.to_metadata()
          self.assertEqual(metadata, {
              'javascript': 'x = 1;',
              'source_url': '',
          })
  
subject: Add basic test for jsbox forms.