Integration Testing
Most defects live in the handoff between systems, not inside either one alone. GullySystem tests what happens when your software talks to a payment gateway, a messaging API, a courier partner or your accounting system.
The Failure Nobody Owns
Your application works. The payment gateway works. The courier's tracking API works. The defect appears only where the three meet — an order marked paid before the gateway confirms it, a shipment created twice because the courier's response arrived late, an invoice that never reaches the accounting system because a field name changed on one side. Each vendor tests their own piece; nobody but you has a reason to test the join.
What Gets Tested at Each Join
Successful Handoff
Data leaves one system and arrives correctly and completely in the next, in the format the receiving side actually expects.
Timeout and Failure
What your software does when the other side does not answer in time, answers with an error, or answers twice for one request.
Ordering and Duplication
Whether a retried call or an out-of-order response can create a duplicate order, a duplicate shipment or a duplicate ledger entry.
Data Mapping
Whether a field means the same thing on both sides — a status code, a currency, a tax category — so nothing is silently misread.
How It Is Run Without Touching Live Accounts
Testing runs through sandbox or test accounts for each connected service, so a failure scenario can be forced safely — a declined card, a courier API returning an error, a message that never delivers — without affecting a real customer, a real shipment or a real ledger entry.
A Coworking Space's Booking Platform, as an Example
A coworking operator's booking system charges a card, notifies the member on WhatsApp, and posts the invoice to its accounting software. Testing forces the payment to succeed while the WhatsApp notification fails, forces the accounting post to happen twice for one booking, and checks a member cancelling in the exact window the payment gateway is confirming the charge — the moments a demo never reaches but a real day eventually will.
Frequently asked questions
Which integrations can you test?
Payment gateways, WhatsApp and SMS messaging, courier and logistics APIs, accounting systems, CRM platforms and any other service your application calls, provided a sandbox or test account is available or can be arranged for it.
What happens if a third-party service has no sandbox?
We test as much of the interaction as possible using recorded or mocked responses that reproduce success, failure and timeout conditions, and flag clearly which scenarios could only be confirmed against a live account, so that gap is known rather than assumed covered.
Do you test integrations built with iPaaS tools like Zapier or Make?
Yes. The workflow itself is tested the same way as custom code — valid and invalid input, what happens when a step fails partway, and whether a retried run creates duplicate records downstream.
What drives the cost of integration testing?
How many external systems are connected, how many failure and retry scenarios need coverage per integration, and whether sandbox accounts already exist or need to be set up as part of the work.
What decides how long integration testing takes?
Mostly how many integrations are in scope and how quickly sandbox access is issued by each third party. Some payment and courier providers take longer to approve test accounts than the testing itself takes to run.
Do you need our live vendor accounts to test this?
No. Testing runs on sandbox or test-mode accounts for each connected service specifically so failure scenarios can be forced without risk to a real transaction, a real shipment or a real customer message.
Tell us what you need.
Send a short brief and one of our engineers will come back to you — usually the same day.
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