Mongodb: failed to connect to server on first connect : <p>I get the following error:</p>

<pre><code>Warning { MongoError: failed to connect to server [mongodb:27017] on first connect
    at Pool.&lt;anonymous&gt; (/Users/michaelks/Desktop/users/node_modules/mongodb-core/lib/topologies/server.js:325:35)
    at emitOne (events.js:96:13)
    at Pool.emit (events.js:188:7)
    at Connection.&lt;anonymous&gt; (/Users/michaelks/Desktop/users/node_modules/mongodb-core/lib/connection/pool.js:270:12)
    at Connection.g (events.js:292:16)
    at emitTwo (events.js:106:13)
    at Connection.emit (events.js:191:7)
    at Socket.&lt;anonymous&gt; (/Users/michaelks/Desktop/users/node_modules/mongodb-core/lib/connection/connection.js:173:49)
    at Socket.g (events.js:292:16)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at connectErrorNT (net.js:1025:8)
    at _combinedTickCallback (internal/process/next_tick.js:74:11)
    at process._tickCallback (internal/process/next_tick.js:98:9)
  name: 'MongoError',
  message: 'failed to connect to server [mongodb:27017] on first connect' }
</code></pre>

<p>Even though I get this in the terminal window where I run Mongo:</p>

<pre><code>2016-12-25T03:45:23.715+0100 I NETWORK [initandlisten] connection accepted from 127.0.0.1:58868 #8 (8 connections now open) 
</code></pre>

<p>It kinda looks like there is a connection..</p>

<p>I've tried both</p>

<pre><code>$ mongod 
</code></pre>

<p>and</p>

<pre><code>$ brew services start mongo 
</code></pre>

<p>This is my test_helper.js</p>

<pre><code>const mongoose = require('mongoose');
mongoose.connect('mongodb:localhost/users_test');
mongoose.connection
 .once('open', () =&gt; console.log('Good to go!'))
 .on('error', (error) =&gt; {
 console.warn('Warning', error);
 });
</code></pre>

<p>I have not specifically made the db "users_test" as I am under the impression that mongoose or mongo or both will do this on the fly.</p>

<p>I've tried both "localhost" and "127.0.0.1​".
I'm on OSX 10.11.5
I'm running Node 7.3.0 and Mongo 3.2.9</p>

<p>What am I doing wrong? How do I figure out what's wrong?</p>
