message: adding a test
  (turned out to already be passing because I guessed wrong, but the test is fine to keep)
diff: @@ -330,7 +330,7 @@ describe('schema/validation', function() {
  type: 'fields',
  id: 'primary-image',
  attributes: {
  - fieldType: '@cardstack/core-types::belongs-to'
  + 'field-type': '@cardstack/core-types::belongs-to'
  }
  }, null, null);
  let errors = await schema.validationErrors(pending);
  @@ -357,6 +357,19 @@ describe('schema/validation', function() {
  expect(pending.finalDocument.attributes.timestamp).equals('2017-03-14T14:50:00Z');
  });
  + it("returns modified schema when validating a schema change", async function() {
  + let pending = new PendingChange(null, {
  + type: 'fields',
  + id: 'extra-field',
  + attributes: {
  + 'field-type': '@cardstack/core-types::belongs-to'
  + }
  + }, null);
  + let newSchema = await schema.validate(pending);
  + expect(newSchema).is.ok;
  + expect([...newSchema.fields.keys()]).contains('extra-field');
  + });
  +
  });
  function create(document) {
  