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What is Integration Testing?

  • Pragya Soni
  • Mar 30, 2022
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‘Good software, like wine, takes time.’

– Joel Spolsky


A software is not merely a series of codes and programs stitched together. It is more or less the soul of hardware. Devices and appliances are nothing without the software. Embedded software brings the functions and versatility to the devices. 


Defining software for you, a software is basically the inner system of devices, that helps in operating functions, can be called an operating system too. Unlike hardware it can’t be touched or seen. But even a minute bug in it can cause a big lapse in the hardware. 


And, as said by Joel, making software is similar to the wine making process. It requires time and attention. Before setting or launching a software it has to pass several tests and experiments. In this blog we will study about integration testing, which is basically a software testing step.


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What is Software Testing?


Software testing is divided into two basic steps, unit testing and integration testing. Integration testing is the second step to follow in software testing. In unit testing each feature of software is tested in a solo test along with the devices. While in integration testing the device and features are tested in groups.

As the name itself suggests, integration testing, where testing is done after integrating the whole device, system or software. The aim of integration testing is to check the sincerity of communication between all the modules.

Modules are the part or feature of a software. A software is designed by combining different modules. In short terms modules are basically the part of a software program. It can be designed by different programmers or the same one.

Before launching the software, the team combines all these modules into one proper program which is ultimately known as software. Unit testing tests the modules separately and integration testing combines all these modules before the test.

After checking the working of modules independently, it is essential to record a check on their dependent factors. Like how does the data flow between one module to another.


Guidelines for Integration Testing


Here is the list of proper guidelines that must be followed before integration testing.


  1. Integration testing can be done only if the functional testing on each module is performed.


  1. Integration testing is always done in sequence. Like you have to pick modules in order to avoid complications and competitions.


  1. Before performing the test on the module. study goes well through the case data. Like what is the need of this test and the requirements that need to be fulfilled for this test.


  1. Determine and examine the structural and architectural application of the module as it is crucial for testing.


  1. Verify each interface in detail before applying integration testing.


  1. If you find any bugs in the program, report to the programmer and developer to fix the defects.


  1. Emphasize on positive and negative integration testing.


  1. Choose and manage input data before actually executing the program. As input data is a crucial element of the software.


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Positive Integration Testing and Negative Integration Testing


Point 7 in the guidelines might have worried you about positive and negative integration testing. Well, the common difference between the two terms is mentioned as:


Positive Integration Testing


An integration testing is said to be positive only when it passes the command given, when the program works in the way it is asked to, it passes the test. And the test is said to be positive integration testing.


Negative Integration Testing


When the test fails to deliver the task, it is asked to. The software fails the integration test. There the test is known as negative integration testing.



Examples of Integration Testing


To understand the integration testing more better, let us consider a common examples related to it:


Suppose you work for an IT organization. And your company has been asked to develop and design an online shopping website for a client, who wants to sell his clothes online through the site.


First you will gather the company requirements, like whatever it needs. After gathering the requirements, you will design the layout of the site. The basic requirements are:


  1. User or admin login.


  1. Catalog of different outfits.


  1. A shopping cart.


  1. Billing details corner.


  1. Payment gateway.


  1. Package tracking.


  1. Shipping tracking.


Thus, now each of these tasks would be assigned to different developers. Like one developer will design the icon, the other will work on establishing a secure payment gateway, one will design a catalog counter and another for the admin login. 


Once each developer is done with his assigned task, it begins to check its individual functionality. Thus, they work on their respective modules. After each module is completed, it is combined together.


Unit testing is done, but now after combination, once again the program and software is checked to calculate and analyze data flow between different modules. This is what we call integration testing.


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Different Approaches for Integration Testing


Integration testing is classified on the basis of approach. There are two approaches for integration testing, incremental approach and non-incremental approach. Here is the basic introduction to both the approaches:

Approaches of Integration Testing1. Incremental approachA. Top-Up approachB. Bottom-down approach2. Non- Incremental Approach

Approaches of Integration Testing


  1. Incremental Approach


Incremental approach as the name suggests is followed in ascending order. Modules are arranged in one-by-one order as per the need and requirements.


But the modules must be arranged logically and be related in all aspects. An even incremental approach is a form of integration testing. Thus, it is done by combining two or more modules together. It determines the correctness of functions.


Incremental approach continues until successful testing of all the modules. First two modules are taken and tested, if the data flow between them goes well another module is added. Again, the test is performed.


 The incremental approach is further classified into two types, Top-down approach and bottom-up approach.


  • Top-down Testing


The top-down testing strategy checks the details of the software. It deals with the process in which higher level modules are tested with lower-level modules. This approach helps in detecting the major design flaws and defects.


  • Bottom-up Testing


The bottom-up testing strategy checks the process in which lower-level modules are tested with higher level modules. It is the opposite of top-down testing. Thus, in this process top level critical modules are tested at the last.



  1. Non-incremental Approach


The non-incremental approach is a complex approach of integration testing. It is also known as the big bang method. It is applied in the cases where the identification of parent data and child data.


In a non-incremental approach the data is banged on different modules. Modules are added from bottom to top to check the data flow in the same order.


Non-incremental approach is employed for small size software systems, unlike, incremental approach which is appointed for large size software.


Though, the identification of defects is complicated in this approach as the source of the bug can't be traced. Also, sometimes small modules are skipped in the process.


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What is Black Box Testing and White Box Testing?


Back box testing and white box testing are the forms of integration testing. Integration testing has several varieties including, black box testing and white box testing. The key points of both the terms are:


Black Box Testing


Black box testing is integration testing that is done on the system with no prior knowledge of its internal workings. Black box testing is done by hiring a tester, that may be related to the field or maybe not.


The tester feeds an input via the software. Later he observes if the output is obtained as per the input or not. This helps the team to identify the response action of the software. It also helps in detecting the response of software to expected and unexpected user actions.


Thus, black box testing is a powerful testing technique used to detect the response, usability issues and reliability capacity of the software. It is like an end-to-end service of the system. 


An example of black box testing is dynamic application security testing, abbreviated as DAST. The programs are expected to receive the accurate response as per the request. If it passes and delivers the promises to the program to pass the test, it is positive.


Following techniques are involved in black box testing:


  • State transition technique


  • Decision table technique


  • Boundary value analysis


  • Cause and effect testing


  • Equivalence testing


  • All pairs analysis and testing


  • Error guessing


White Box Testing


White box testing is a form of integration testing that is basically done by the professors and technicians. White box testing has other names too like glass box testing, structural testing, open box testing, and transparent box testing.


White box testing tests the internal coding and infrastructure of the software. It is done to check the predefined inputs against expected and desired outputs. White box testing is to find and spot the inner workings of the software. It involves several internal structure testings. But it requires several programming skills to design test cases.


The aim of white box testing is to focus on the flow of inputs and outputs through the software. It also helps in strengthening the security of the software. Just like its name, it represents a clear box that has the ability to see through its inner workings.


Techniques involved in white box testing are as follows:


  • Data Flow testing


  • Branch Coverage testing


  • Control Flow testing


  • Decision Coverage testing


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Why is Integration Testing Essential?


You might be wondering why integration testing is done even when unit testing is performed before on software. The reasons for which integration testing is essential for software are:


  1. Even after unit testing few errors are left in the program that can't be traced. Integration testing is essential to remove those bugs from the program.


  1. While developing a software, each module is developed by different programmers. So there may be a logical difference between them creating a syntax or logical bug during the execution of the program.


  1. Integration testing is essential to check the interaction of software modules with the database.


  1. Integration testing is essential to check the compatibility of hardware with software.


  1. After integration testing the requirements can be checked and modified as per as the need.


Thus, integration testing is mandatory to check the incompatibility and lags between different modules.


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Despite the listed approach, there are several other approaches too. For example, Big Bang integration, system integration and component integration. There is no doubt that integration testing is an essential part of software testing. And is responsible for completing the launch of the software.

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