Example usage.

var helper = require('dl-test-helper');

var reqParams =  {
    "q": {
        "querystring": "categories  AND excluded_categories",
        "keys": {
            "categories": "f3594bf6-a801-422d-8528-c0a26c5d27ad",
           "excluded_categories" : ["89d48198-a09f-4823-83af-d41f60599392", "a780fae0-d118-4bdb-bb9f-71d5f43c595b"]
        }
    }
};
        
        
// Where to send 
var request = {
    identity: 'test.onetapi.pl',
    interface: 'ro.stuff.something.onetapi.pl',
    method: 'search',
    params: reqParams
};

// Send 
helper.sendOpalRequest(request, function(err, result) {
    if (err) {
        //do smth
        return;
    }
    //result is an object
    console.log(result.response.numFound);
})