nightwatch custom command callback - postgresql

Question

I'm trying to create a custom command in nightwatch that runs a query on a Postgres database and returns the result. The query runs just fine and outputs the result to the console but then the execution of the test stops. I don't understand how callbacks work. How can I fix this custom command?
exports.command = function(sql, callback) {
var self = this;
var pg = require('pg');
var conString = self.globals.testinfo.connectionString;
var db = new pg.Client(conString);
db.connect(function(err) {
if(err) {
console.error('could not connect', err);
}
else {
db.query(sql, function(err, result) {
if(err) {
console.log('error running query', err);
}
else {
console.log(result.rows.length);
db.end();
}
});
}
}),
function(result) {
if (typeof callback === 'function') {
callback.call(self, result);
}
}
return this;
};

Answer 1

I had to wrap the database connection in a perform command to get this working. I'm not sure if this is the best way to handle the callback, but it works. Here's the updated version of the custom command:
exports.command = function(sql,callback) {
var self = this;
var pg = require('pg');
var cs = self.globals.testinfo.connectionString;
self.perform(function(self,done) {
pg.connect(cs,function(err,db,done) {
if(err) {
return console.error(err);
}
db.query(sql, function(err,result) {
done();
if(err) {
return console.error(err);
}
console.log(result.rows.length);
callback(result.rows[0]);
});
});
pg.end();
done();
});
};
Here's how I call the custom command in the test:
browser.myCustomCommand('select * from table limit 1;', function(row) {
browser.assert.deepEqual(row.column,'some value');
});

Answer 2

Can you try this:
exports.command = function(sql, callback) {
var self = this;
var pg = require('pg');
var conString = self.globals.testinfo.connectionString;
var db = new pg.Client(conString);
var cb= function(result) {
if (typeof callback === 'function') {
callback.call(self, result);
}
};
db.connect(function(err) {
if(err) {
console.error('could not connect', err);
cb(false);
}
else {
db.query(sql, function(err, result) {
if(err) {
console.log('error running query', err);
cb(false);
}
else {
console.log(result.rows.length);
db.end();
cb(true);
}
});
}
}),
return this;
};
And in your test :
'test' : function(browser){
browser.yourCommandName(sql,function(result){
console.log(result); //if connect is good result would be true and false if fail to connect.
});
}
Ps: the result in callback can be as an object(contain rows or anything you want), instead of boolean only in this example.
And Nightwatch is used for end-to-end testing, it is not aimed for Database testing,i think you should find another framework to test database connection.