如何通过从 mongo db 检索到的 object 到 javascript 中的测试

Question

I am working on NodeJS test automation project. My goal is to get data from Mongo DB and use it in the tests. I successfully query the data from the DB, but so far I've failed to transfer the values to the test.

My Mongo DB halper (mongodbHelper.js):

var MongoClient = require('mongodb').MongoClient;
var url = "myurl";

var data;
const getTestData =  async function(){
    MongoClient.connect(url, function(err, db) {
        if (err) throw err;
        var dbo = db.db("mydb");
        dbo.collection("my_test_collection").findOne({"testId": "test_01"}, function(err, result) {
            if (err) throw err;
            db.close();
            data= result;
            console.log(data); // This print prints correct data
            return result;
        });
    });
}

module.exports =
{
    getTestData
}

The print inside the handler prints retrieved data correctly. Now I need to use it in the test suite below. I want to initiate the testData variable in Before method and use it in tests. If I do it as below, the print in the test prints undefined. It prints it before the correct print in the helper. So I assume it is a synchronisation problem.

const mongodb = require('./mongodbHelper');
var testData; 

    describe('Playwright with Mocha Demo', function() {
    
        before('name', async function() {
            testData = await mongodb.getTestData();
            console.log(testData); // Here it prints 'undefined'

        });
    ....

Please advise how I can pass the data from the handler to the testData variable in the test correctly.

Answer 1

You aren't returning anything from your async function getTestData .

The Mongo call is asynchronous but you're using a callback function. You could pass a callback function to getTestData and call it with the data (where you're doing the console log). However, the Mongo calls return Promises, so you could just do something like this:

const getTestData = async function() {
    const db = await MongoClient.connect(url);
    const dbo = db.db("mydb");
    const result = await dbo.collection("my_test_collection").findOne({"testId": "test_01"});
    db.close();
    return result;
});

Then in your test you can retrieve the data with:

testData = await mongodb.getTestData();