`index.test.js` throwing unhandled exception

[makinde]

index.test.js
(node:87895) UnhandledPromiseRejectionWarning: MongoError: ns not found
    at /Users/goldstein bryan/workspace/mongoose-authz/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:593:63
    at authenticateStragglers (/Users/goldstein bryan/workspace/mongoose-authz/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:516:16)
    at Connection.messageHandler (/Users/goldstein bryan/workspace/mongoose-authz/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:552:5)
    at emitMessageHandler (/Users/goldstein bryan/workspace/mongoose-authz/node_modules/mongoose/node_modules/mongodb-core/lib/connection/connection.js:309:10)
    at Socket.<anonymous> (/Users/goldstein bryan/workspace/mongoose-authz/node_modules/mongoose/node_modules/mongodb-core/lib/connection/connection.js:452:17)
    at Socket.emit (events.js:180:13)
    at Socket.emit (domain.js:422:20)
    at addChunk (_stream_readable.js:274:12)
    at readableAddChunk (_stream_readable.js:261:11)
    at Socket.Readable.push (_stream_readable.js:218:10)
    at TCP.onread (net.js:581:20)
(node:87895) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 5)
(node:87895) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.