Integration Testing

Integration Testing,  

• It is defined as a type of testing where software modules are integrated logically and tested as a group. A typical software project consists of multiple software modules, coded by different programmers. 
• The purpose of this level of testing is to expose defects in the interaction between these software modules when they are integrated
•  Integration Testing focuses on checking data communication amongst these modules. Hence it is also termed as 'I & T' (Integration and Testing), 'String Testing' and sometimes 'Thread Testing'.
• It is done after Unit Testing
• Integration testing is the process of testing the interface between two software units or modules. It’s focused on determining the correctness of the interface. The purpose of the integration testing is to expose faults in the interaction between integrated units. Once all the modules have been unit tested, integration testing is performed.

Strategies used in Integration Testing:

• Big Bang Approach 

Big Bang Testing is an Integration testing approach in which all the components or modules are integrated together at once and then tested as a unit. This combined set of components is considered as an entity while testing. If all of the components in the unit are not completed, the integration process will not execute

• Incremental Approach which is further divided into following

• Top Down Approach

Method in which integration testing takes place from top to bottom following the control flow of a software system. The higher level modules are tested first and then lower level modules are tested and integrated in order to check the software functionality.

• Bottom Up Approach

Strategy in which the lower level modules are tested first. These tested modules are then further used to facilitate the testing of higher level modules. The process continues until all modules at top level are tested. Once the lower level modules are tested and integrated, then the next level of modules are formed.

• Sandwich Approach - Combination of Top Down and Bottom Up

Strategy in which top level modules are tested with lower level modules at the same time lower modules are integrated with top modules and tested as a system. It is a combination of Top-down and Bottom-up approaches therefore it is called Hybrid Integration Testing. It makes use of both stubs as well as drivers.

Advantages:

• Integration testing provides a systematic technique for assembling a software system while conducting tests to uncover errors associated with interfacing.
• The application is tested in order to verify that it meets the standards set by the client as well as reassuring the development team that assumptions which were made during unit testing are correct.

 

Disadvantages:

• Fault Localization is difficult.
• Given the sheer number of interfaces that need to be tested in this approach, some interfaces links to be tested could be missed easily.