Integration Testing: Here is a Comprehensive Guide

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Hello, welcome to our blog post on integration testing.

Every software has a design and goals of satisfying its end users. These software products are often built from different modules or components which need to meet certain standards for top quality outcomes.


For a software product to meet the required standards, it needs more than just the common design, code and launch process. It must be put to test to enable an evaluation of the product and verification on how it meets user demands.

This is why integration testing is very important. According to the Katalon Studio, integration testing helps in pinpointing conflicts in software. These conflicts include issues of incompatibility, data format and different processing logic.

Understanding the Importance of Integration Testing

Integration Testing Definition

In software testing, what is known as integration testing is a testing practice that involves both integration and testing. It is a testing method whereby different software units and components are brought together for testing.

Please note: all individual modules or components may or may not be coded by the same person/team.

The ultimate importance of integration testing is to evaluate the interfaces of the modules or components in search of defects. The defects identified in integration testing are not the common types. They are those defects which develop as a result of integration and interactivity.

The Importance of Integration Testing

Here is the thing with software and software testing. Different important modules or components may work perfectly at individual levels.

They may even pass unit testing. However, when they are combined under integration testing to test how they perform as a unified body, Boom, they fail.

This is why integration testing is important.

Let us take a deeper look with some points below;

Integration Testing Deals with Issues of Inconsistent code logic

When a software product is coded by different programmers, they will make use of different approaches and logics. At individual levels the codes or program will work well but may misbehave when put together.

In most cases, this results in functional and usability issues. The solution to fixing such issues to meet the software design and user requirement is to implement integration testing.

The testing method ensures that all the codes in each component are well aligned. This in the end leads to a well working software that meets user expectations.

Solves Issues of Shifting Requirements

Software development is not an easy job as there are several complexities, especially with dynamic behaviours from clients.

For example, in the middle of the software development stage, a client may decide to change certain requirements. Now the programmers and the development team need to make all the needed adjustments to meet the needs.

The tech expert contributor, Katalon, says most times when this happens, the development team will need to do some serious modification of codes. “Modifying the code of 1 module to new requirements sometimes means changing its code logic entirely, which affects the entire application”.

Integration Testing Takes Care of Erroneous Data

In software development there is collaboration among teams. This means there will be a need for transfers of data across different modules or components.

Sometimes the data transfer may not be properly handled so some issues may arise. Issues related to processing and reading are very common in this case. This results in bugs.

What to do when this problem arises? You guessed right. Implement integration testing takes care of all of such issues.

The importance of integration here is to help you in pinpointing where the issues come from so that you properly troubleshoot.

It is Important for Third-party Services and API Integrations

We mentioned in the previous point that data transfer may come with some issues, which include changes in data.

This usually leads to the API and third party receiving wrong or false data. When this happens, they will also generate false outputs which will not be good for your business.

You can fix this by implementing integration testing because it ensures better and improved communication.

Code Exceptions

When developers are inadequate in accounting for exceptions in their codes, you will need to make this easy for them by bringing all components together. This is another importance of integration testing.

Hardware interfaces

You may encounter software-hardware compatibility issues which will come with annoying bugs. Thanks to integration testing, you can easily fix this.

Here is a summary of the importance of Integration Testing

  • Software is composed of a vast network of smaller parts. By performing integration testing, we make sure that they cooperate to provide the desired functionalities.
  •  Integration testing is necessary because modern software must communicate via APIs with a variety of external systems to provide specific functionalities.
  •  The importance of integration testing is to check the system’s overall information flow and data flow.
  •  Also, it plays an important role in increasing assurance in system behaviour, particularly if shift left testing is used early on in the testing life cycle.

Integration Testing Process: What Does Integration Testing Look Like?

It is simply the integration of different modules or components to test how they work together.

In other words, integration tests how each component interacts or behaves when combined. To this end, the testing method is able to accurately verify how and if they are working as they ought to.

An effective and standard integration testing process involves the use of test drivers and stubs. These are otherwise known as dummy programs and their work is to, as Techtarget puts it; “act as substitutes for any missing modules and simulate data communications between modules for testing purposes.”

Integration Testing or System Integration Testing Tools

There are several system integration testing tools or integration testing tools if you like. These tools are important for producing the best results. They may include the following;


This is one of the most common and easy-to-use integration testing tools out there.  It is free and open source and it offers automation testing for software products.


This is an offshoot of the powerful Python software. It is therefore also a powerful testing tool and it enables integration testing to be easily done. Pytest offers automation features and functions that makes the whole process hassle-free for testers. says that as simple as the tool is, it offers strong support for “complex functional testing for applications and libraries”.

IBM’s Rational Functional Tester (RMF)

Another important one of the system integration testing tools is the RMF. This one is object-oriented but will have full automation features for testing. It is useful for regression testing, functional testing and even GUI testing. Plus, with this tool, you can perform data-driven testing.


Like the Selenium testing tool, this system integration testing tool is free and open source. It has a framework that is designed for Java and Java Virtual Machine. So, if you want to perform Java-based integration tests and you need a Java-supporting tool, you know where to look.


This is also another reliable Java-based tool. It is also open source.


This is one of the non-system integration testing tools for JavaScript. It has proven to be reliable to testers.


Here is another open-source system integration testing tool that stands out for its capacity to enable strong collaboration among teams. Techtarget says the tool allows “developers and customers to work together to build test cases on a wiki.”


This is a powerful software test from GitHub and as expected, it is a free and open-source framework. However, it is dedicated to JavaScript-enabled web apps.


It is ranked among the best system integration testing tools that is adopted by organisations. Especially when it has to do with verification and compliance.

What is Top Down Integration Testing?

Top-down Integration testing is an incremental testing approach that moves from top to down, just as its name implies. As it moves, it integrates modules and tests them. The concept of incremental testing is very important in understanding top down integration testing.

Top-down integration testing example as Illustrated by Lamdatest

Lamdatest describes the Top-down integration testing with a clear example;

Let us say these are the modules that make up our application under construction; a login page, a profile page, and a data record page. Also, all three contain all the information related to the user’s transaction.

First, we will record all user data and test them. This will be followed by the Profile Page, and finally all three in the top-down integration testing methodology.

A few items from the Profile module are required to test the data records module, and in order to obtain Profile, you must have the necessary login information. At this stage of the test, you can use Stubs

The login page module does not directly interact with you at this point, but the modules above can still receive the right response.

The module connections shown here may not be as straightforward in real-world scenarios as they appear to be.

Is Incremental Testing A Core Part of Top Down Testing?

The answer to the question is simple; yes, it is! It is a high-level approach and it works in a very amazing way. Incremental testing enables testers to use the module-by-module approach. This you can otherwise call, a one-by-one method in an incremental way.

According to Lambsates “The main aim of performing incremental integration testing is to reach an integrated stage (one by one) no matter which way you travel”. So, testers can start incremental testing from any module and move incrementally towards the last one – the end.

Advantages of Top Down Integration Testing

The top down integration testing method has some interesting benefits that you must know. These are good for your project and system.

Top Quality

Everything about the top down integration testing leads to producing a quality product.

Good for early testing

The top down integration testing type is suitable and efficient for early tests. This benefit also plays a vital role in ensuring quick time to market.

Control Process Identification

Top down integration testing allows for the identification and control of processes, especially on data flow. With this, there is always clarity on the system.

The Bottom-up Integration Testing Example

Different from the top down integration testing, the bottom up integration testing is a testing method that goes from low to high levels. In other words, it goes from dependent modules to independent modules.

Explaining the bottom-up integration testing example, a Linkedin post with the title, “What are the Benefits of Using a Bottom-up Approach for Integration Testing?” has this to say; “if you have a system that consists of a user interface, a business logic layer, and a database layer, you would test the database layer first. After that, then “integrate it with the business logic layer, and finally with the user interface”.

Benefits if Bottom-up Integration Testing

Early Testing

Bottom-up integration testing enables early testing for best results. You can use this testing approach to perform integration testing whereby you test the following;

  • Test functionalities
  • Test performance of important modules

Find and fix any flaws

This can assist you in finding and correcting any flaws or errors in a system’s fundamental parts before they have an impact on the modules at a higher level.

Decreases Reliance on Drivers and Stubs

Bottom-up integration testing can lessen the need for drivers or stubs, which are simulated elements that simulate the behaviour of the modules that aren’t yet available for testing.

Stubs and drivers may not accurately reflect the actual functionality of the modules they replace and can add complexity and overhead to the testing process.

Difference between Top Down and Bottom-Up Integration Testing


For top down testing, the performance moves from the top module to the lower ones. In the bottom up, however, the movement is from the lowest module to the top one.

Module Priority

In the top down method, there are submodules but they are developed only after the main ones have been developed. Bottom up on the other hand, give preferences during the development process.

Time of Performance

Both approaches have different styles of operation. For example, the top-down testing method performs when the errors or bugs are higher at the top module. Bottom up on the hand, goes through the lower modules.


Both techniques are also different in terms of usage. For example, top down uses stubs while the bottom up uses drivers.

Which Scenarios Demand for it

Top down testing appears to be advantageous if the programme is built in a structural or procedural manner. 

Bottom-up testing appears to be preferable if the program is written in an object-oriented manner because it makes it easier to develop smaller modules first.

Learning and Execution difficulties

It is discovered that top-down testing is less complex than its counterpart. Bottom up is a little more difficult to learn and master because of its complexity.

Integration Testing Conclusion

In this blog post, we have revealed a lot to you. We have broken several concepts to their simplest forms for your understanding.

From all that we have revealed, one thing is sure; integration testing is one of the most important methods of software testing.

It must not be taken for granted and should be implemented early enough in the software development life cycle. The technique is important because it works in different ways but with the goal of helping you create the best quality software product for your stakeholders.

We highly recommend you hire testers who have the knowledge of incremental testing and will deliver your project as it should be.

Harish Rajora would say depending on the tester’s choice, integration testing can either be achieved by moving depth-wise or breadth-wise.


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