Creating a software application meant for simplifying human tasks is ironically involves many professionals.  

This effectively means that individual parts of a complex application may be coded differently. But they need to work together effectively to bring out the optimal functionality of the software.  

Alternatively, with the advent of Fintech applications, APIs, and other such software which communicate with each other to link several functionalities, the developers and testers need to ensure a seamless user experience is provided.  

These are two important reasons why Integration Testing is an important step in the software industry today.  

What is Integration Testing  

Individual software modules are first tested as a unit, known as unit testing. Once they are good to go, they are tested together, to see if their interaction with each other serves the desired output of the module/software properly.  

This is known as Integration Testing.  

For example, think of a manufacture of a automobile where individual parts like engine, clutch and gear box, brake system and wheels have to be tested individually and then have to be integrated properly to ensure functionality (optimum performance while driving).  

Why Integration Testing is Necessary  

The chief purpose of Integration Testing is to evaluate the interfaces between different modules of the software and check for their behavior as a unit. Testing would also unearth any possible bugs which might impede proper working of the software.  

The best Integration Testing is one where the functionality of the app is checked properly, bugs are identified and resolved within a short period of time.  

This is an important check to ensure that the structure of data does not change while it moves from one software module to another.  

In case any software is integrated with third-party tools or APIs, integration testing is necessary to ensure a seamless experience for the customer.  

For example, payment options provided to customers on a e-commerce platform or an online insurance portal should work properly when the customer proceeds to check-out. A bad integration can ruin the customer experience and lead to loss of brand value and customer growth.  

To quote a real-life example, a leading American e-commerce application wanted a quick integration testing of their app with SFCC, SFOM, WMS, and Avalara validations. Aspire was able to support more than 25 production releases with a zero-defect Integration testing in a short time frame.  

Integration Testing is also handy to identify potential gaps which might arise due to frequent upgrades to software, which is a demand in today’s landscape. It would be difficult to unit-test every time an upgrade is added.  

The following can provide challenges to Integration Testing:  

  • When legacy systems are integrated with new applications 
  • Integrating applications from two different organizations  
  • Issues pertaining to database, environment, and platform used 

Types of Integration Testing

The best type of Integration Testing is the one that is parallelly done with development, in keeping with the DevOps methodology.  

But this can be modified suitably based on the requirements of each project.  

The types of Integration Testing are:  
  • Big Bang testing 

This is where all modules are integrated at once and tested. The advantages of this type of testing is that it can be finished quickly which helps in faster deployment of the application.  

However, this is advantageous only if the system being tested is a small one. For larger systems, testers have to wait till all modules are coded which gives them less time to identify errors and rectify them. There is also little room for priority testing of user interfaces and high-risk modules.  

  • Top-down testing 

In this method, the higher-level module is tested first followed by the lower-level modules. Though this is advantageous for priority testing of critical modules, the lower-level modules are at a risk of being under-tested.  

  • Bottom-up testing 

The reverse of Top-down model, the lower-level modules are tested first, followed by the higher-level one. This method makes the best use of time as smaller modules are tested as soon as they are developed. However, the critical modules, the higher-level ones, are tested last and hence might be prone to defects/errors/bugs which can be a risky proposition.  

  • Mixed/Sandwich/Hybrid type testing 

This combines the Top-down and bottom-up types of testing.  


Integration Testing is important to ensure the fine working of individual units of a software, coded by different human resources, boxed together. Units might work well standalone, but interactions with other units, data flow, and other such integrations can bring about bugs or errors in the working of the application as a whole. With the advent of online payments and shopping, payment applications, tax applications, and other Software as a Service (SAAS) applications need to be integrated with base applications. This has to work well to provide a seamless experience for the user, which necessitates Integration Testing.  

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