External interface testing or Intersystem testing is the process of testing the integration points of single application or software hosted at different locations and then confirming the correct data flow across the different locations. It validates the system based on how the different systems are interconnected to complete the end to end flow of the control and data. The applications are interconnected to other application systems. External interface testing ensures the interconnection between the application functions correctly. The multiple applications involved are sometimes called as cycles or functions.
For example, the shopping sites, air ticket booking sites, etc are linked to payment sites like paypal.com with payment functionality. Another example, the social networking sites have advertisement links to shopping sites.
The main objectives of this external interface testing are:
- Accurate parameters and correct data are passed between different applications.
- Documentation for required applications is correct and organised and correct in all details.
- Having proper timing and coordination between the applications. For example Loan system software is sharing the database with accounting system software in the banking sector and in Shopping mall billing system and bar code reader is interconnected with each other.
The user can purchase products on eBay.com by searching the product, selecting product, selecting paypal as payment option. The paypal.com page opens. The user logs into the account and makes payment. If payment is successful, the order details are displayed on eBay.com. External interface testing is to test the payment functionality that links eBay.com and paypal.com.
Check your understanding:
1. What is the use of Intersystem testing?
2. What are the advantages and disadvantages of intersystem testing?