exports['Should correctly find one document with custom fields and undefined callback'] = {
  metadata: {
    requires: {
      promises: true,
      topology: ['single']
    }
  },
  test: function (configuration, test) {
    var db = configuration.newDbInstance(configuration.writeConcernMax(), {
      poolSize: 1,
      auto_reconnect: false
    });

    db.open().then(function (db) {
      var collection = db.collection('findOneDocumentCustomFieldsUndefinedCallback');
      collection.insertMany([{
        a: 1,
        b: 1
      }, {
        a: 2,
        b: 2
      }, {
        a: 3,
        b: 3
      }, {
        a: 4,
        b: 4
      }], configuration.writeConcernMax()).then(function (result) {

        // Show that duplicate records got dropped
        collection.findOne({
          a: 1
        }, {
          fields: {
            b: 1,
            _id: 0
          }
        }, undefined).then(function (item) {
          test.equal(item._id, undefined);
          test.equal(item.b, 1);
          test.equal(item.a, undefined);
          db.close();
          test.done();
        });
      });
    });
  }
}