Software Testing Methods – What is Integration Testing?

Kategorien Functional Testing, Integration Testing, Software Development, Software Testing

On my side project where write test´s for a RESTAPi with Spring Boot. I finished writing Unit Tests for The RESTApiController but now I want to learn what Integration Tests are and why we need them.
So I decided to write a blog post about it since i´m doing the Software Testing Types and Method blog series. Let´s start of

What are Integration Test?

Integration testing is a critical phase in the software development process in which individual units are combined and tested collectively, with a focus on the interfaces between applications.
This typically occurs after unit testing has been completed and before system testing, providing a bridge between software functionality and full system operation.


For example you have to test the keyboard of a computer than it is a unit testing but when you have to combine the keyboard and mouse of a computer together to see its working or not than it is the integration testing.
So it is prerequisite that for performing integration testing a system must be unit tested before.

Advantages of Integration Tests

  • Easy to integrate with daily builds and easy to test in development environment
  • Code Coverage is higher and easy to track.
  • Tests are more reliable and easy to isolate the failures.
  • Tests run faster compared to end to end tests.

Strategies of Integration Testing

  • Big Bang approach
  • Incremental approach
    • Top Down approach
    • Bottum up approach
    • Sandwich approach -> Top Down and Bottom Up combination

Big Bang Integration Testing

All the modules or components are integrated before and after this everything is tested as a whole.
In this type of testing all units or components are linked at once which result into a complete system. If gives us a complete system after integration which on which we can start testing.


  • Big bang integration testing is used to test the complete system.
  • All the modules are completed before the start of integration testing.
  • Big bang testing is cost effective.
  • If any bug is found it becomes difficult to detach all the modules on order to find out its root cause.
  • This approach is quite challenging and risky, as all the modules and components are integrated together in a single step.
  • Since all the modules are tested together chances of failure increases

Bottom up Integration Testing

Bottom-Up Integration testing is a kind of testing methodology in which the modules are tested from the bottom of control flow upwards. Bottom-Up integration testing is opposite to the Top-down integration testing.
In this testing first the bottom modules of lower levels are tested and then the higher level modules are tested.


  • Fault localization is easier.
  • No time is wasted waiting for all modules to be developed unlike Big-bang approach.
  • Test conditions are easier to create.
  • Early prototype is not possible.
  • The program as a substance does not exist until the point when the last module included.

Top Down Integration

This form of testing involves testing the high level or parent module(s) first, then testing lower level or child modules as development is completed and they are integrated.
Stubs are used to simulate the data response of lower level modules until they are completed and integrated.


  • Fault Localization is easier.
  • Possibility to obtain an early prototype.
  • Critical Modules are tested on priority; major design flaws could be found and fixed first.
  • Modules at lower level are tested inadequately.

Sandwich testing:

It combines the advantages of both Bottom-up testing and Top-down testing at a time.Bottom-up testing starts from middle layer and goes upward to the top layer where as Top-down testing starts from middle layer and goes downward.
Big-bang approach is followed for the middle layer. From this layer bottom-up approach goes upwards and top-down approach goes downwards.

  • Sandwich approach is useful for very large projects having several subprojects.
  • It needs more resources and big teams perform both bottom-up and top-down methods of testing at a time or one after the other.
  • It require very high cost for testing because one part has Top-down approach while another part has bottom-up approach.
  • It cannot be used for smaller system with huge interdependence between different modules.It makes sense when the individual subsystem is as good as complete system.
  • Different skill sets are required for tester at different level as module are separate system handling separate domains like ERP products with modules representing different functional areas.

Thanks for reading through this if you like my content and my way to learn new things let me know.
Ne next blog post will be about Non-Functional Testing so stay in touch with my blog.
Have a great day and keep learning

Moritz Vogt

Credit :


Schreibe einen Kommentar

Deine E-Mail-Adresse wird nicht veröffentlicht. Erforderliche Felder sind mit * markiert.