function testBuilderExec() {
  var propertyReplacer = new goog.testing.PropertyReplacer();
  lf.testing.simulateErrors(propertyReplacer);

  var selectFn = function() {
    return db.select().from(employee).exec();
  };

  return lf.testing.util.assertPromiseReject(999, selectFn()).then(
      function() {
        propertyReplacer.reset();
        return selectFn();
      }).then(
      function(results) {
        assertEquals(0, results.length);
      });
}
Tests that when simulateErrors has been called BaseBuilder#exec() rejects.
@return {!IThenable}