How to test Mongoose CRUD operations with Mocha/Chai? - node.js

Question

I'm trying to test this function, which combs through a database for all unfilled currency trades and checks for a price match. If it finds one, database calls take place to close the trade increment the trader's balance. I pass it an array of prices from another function which is just a series of API calls. This is the function in question:
function executeTrade(pricesArr) {
// currencies array must match up one-to-one with pricesArr array
const currencies = ['btc', 'ltc', 'eth', 'doge'];
let chosen;
// Pull trades from database
return Trade.find().then(dbTrades => {
console.log('foo')
// Get only open trades
const openTrades = dbTrades.filter(trade => trade.open);
openTrades.forEach(trade => {
const balance = `${trade.curr_bought}_balance`;
// Get price to compare
if (trade.curr_bought === 'usd') chosen = pricesArr[0];
else {
for (let i = 0; i < currencies.length; i++) {
if (trade.curr_bought === currencies[i]) {
chosen = pricesArr[i];
}
}
}
// Do math depending on buying BTC with USD or something else
if ((trade.curr_bought === 'usd' && trade.sold_amount >= (trade.bought_amount / chosen)) || (trade.sold_amount >= chosen * trade.bought_amount)) {
// Close trade order
return trade.update({$set: { "open": false }})
.then(() => {
// Update user's balance to reflect successful trade
return User.findOne({"_id": trade.owner}).then(user => {
user.update({
$set: {
[balance]: user[balance] + parseFloat(trade.bought_amount)
}
}).then(doc => {
res.json(doc);
}).catch(err => console.log(err));
}).catch(err => console.log(err));
});
}
});
});
};
I'm trying to test it with this test code:
it('Executes a trade if the specified sell prices are greater than or equal to the reported VWAP', done => {
const pricesArr = [0.1, 1, 1, 1];
executeTrade(pricesArr);
app
.get(`/api/trades/?_id=${testTrade._id}`)
.set('Accept', 'application/json')
.expect('Content-Type', /json/)
.expect(200)
.end((err, res) => {
console.log(res.body);
expect(res.body[0].open).to.be.false;
done();
});
});
The problem is that none of the database calls are executed in the test. The function, and all other tests, work fine in the context of a call to the Express server I'm using to make these calls on the actual web app.
I have even tried executing a simple find operation both in the context of an it() function and out, but neither are every executed.
What am I missing, here?

Answer 1

Because your executeTrade function executes asynchronously, there is no guarantee that the asynchronous calls it contains will complete prior to the next function call (i.e. making the API call in your test). Try something like this instead:
executeTrade(pricesArr)
.then(() => {
// make api call and check expected
});
Which ensures that the promise returned by executeTrade settles prior to running the contents of the "then" block. In addition, you are returning promises inside of a forEach construct, which means again that there is no guarantee that the promised results will be settled prior to the return of the executeTrade function. To fix this, I suggest instead using a pattern like:
return Promise.all(openTrades.map((trade) => {
// do stuff here
});
That will only settle once either all promises returned in the map function fulfill or once one of them rejects.
Finally, it looks as if your executeTrades functions could potentially call res.json() multiple times. You can't respond to the same request more than once, and I also don't see where res is defined in your function, so maybe avoid that too.
Google has a nice guide on promises that I suggest you take a look at.