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Table of contents
Integration Testing
Example of Integration Testing
Need Of Integration Testing
Common Approaches In Integration Testing
Big-Bang Approach
Top-Down Approach
Bottom-Up Approach
Sandwich/Hybrid Approach
Process Of Integration Testing
Integration Testing Tools
Advantages Of Integration Testing
Key Takeaways
Last Updated: Mar 27, 2024

Integration Testing

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Every developer wants to create a logical, workable application supported by several features. To get that done, one needs to check their application against varying test cases to ensure that the application does not crash/fail in any possible situation. In web applications, this is done via software testing. An application goes through several tests before it is presented to the end-user. 

The most common testing includes Unit Testing, System Testing, Integration Testing, Performance Testing, and Acceptance Testing. All these tests are interlinked and help detect errors, improving the application's performance and reliability.

This blog will discuss one such testing, i.e., Integration Testing, in complete detail.

Integration Testing

In this testing, the different components of an application are tested as a combined entity. The main aim of this testing is to test the interface between different components and expose any defect that may arise due to the integration of the components. i.e., all the components working fine individually work after integration as well. This is why it is done right after Unit Testing. In other words, all the components are initially tested individually. Once the unit testing is completed, these components are integrated to check the combinational behavior and performance. This step comes under Integration Testing.

This is to be noted that the Integration Testing does not occur at the end of the cycle, but it is conducted simultaneously with the development. Hence, it is possible that all the modules are not available for testing at a particular instant. This testing is also known as I&T, String, and Thread Testing.

Example of Integration Testing

Consider a music application such as the Spotify Music app. Its main features include sign up/login, various subscription plans, choosing a certain plan, and listening to music.

Once users download the application, they need to enter their respective account information or open a new account (sign-up/login). After completing this step, they are redirected to a page listing multiple subscription plans. A user can choose a plan of their preference and complete the process. 

This is the primary step that needs to be error-free. Otherwise, it can lead to a significant loss for the company. Hence, testers conduct Unit Testing for each unit. Once all modules are available, they are tested together for any bug or data flow error that is a vital step and comes under Integration Testing.

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Need Of Integration Testing

  1. Several individuals work on application components separately. Hence, every unit possesses different logic. This is why it is essential to check the implementation of the logic as per the requirements.
  2. The data structure may get manipulated during the transmission from one module to another, or some value gets appended/removed from the data that can cause an issue in the application.
  3. Modules often interact with APIs and other third-party tools, and hence it is essential to test that the data accepted by these tools is correct.
  4. Most of the time, a developer deploys the made changes without unit testing. At such a point in time, Integration testing plays a crucial role.
  5. Integration Testing also helps eliminate exception handling, data formatting, error trapping, broken schema, mistaken cache integration, etc.
  6. This testing also allows detecting bugs and errors early, saving time and cost.
  7. This testing is capable of developing real-time test cases during end-to-end testing.

Common Approaches In Integration Testing

Four main approaches are used to execute Integration Testing such as:

  1. Big-Bang Approach
  2. Top-Down Approach
  3. Bottom-Up Approach
  4. Sandwich/Hybrid Approach

Big-Bang Approach

This approach includes integrating all components and testing them as a single unit. The integration process does not execute until all the components in a unit are completed.



  • It is suitable for testing small units.
  • It is easy to detect errors in this system. 
  • It saves time and speeds up application deployment.


  • It is challenging to locate the source of error as all the components are integrated as one.
  • This is a time-consuming approach and is not recommended for large applications.
  • Testers can miss some bugs and errors.
  • Testers have to wait until all components are available, giving less time for error analysis and fixing.
  • Due to simultaneous testing, critical and peripheral modules that need to be tested on priority can be missed.

Top-Down Approach

This is an incremental approach. It starts from the topmost module and gradually proceeds to the lowest one. Each component is tested after another and then integrated to test the final functionality.



  • It is easy to detect bugs and errors in this system.
  • The critical units are tested first, which allows in finding major design flaws.
  • It consumes less time compared to other approaches.



  • Testing a lower level may consume a lot of time, so they might not be tested adequately.
  • When too many tests are involved, it becomes problematic.

Bottom-Up Approach

This approach is the exact opposite of the top-down approach. The testing begins from the lowest level and gradually proceeds to the highest one. This approach is preferred when all the modules are available for testing.



  • It is easy to locate errors and their sources.
  • Less time is consumed in troubleshooting as all the required modules are available.



  • Testing all the modules can take up a lot of time.
  • The critical modules are tested at the final stage, so very little time is given for testing and error fixing.
  • If a lot of lower-level units are present, testing can become complicated.

Sandwich/Hybrid Approach

This approach is a combination of both top-down and bottom-up approaches. The top-level units are tested separately, whereas the low-level units are examined after integrating with the upper-level units.


  • This approach is preferred for testing huge programs and long-term applications such as operating systems.


  • It is very complex and costly.
  • A higher level of precision and skills are required for this approach.

Process Of Integration Testing

Integration Testing follows the steps listed below:


  1. Prepare an integration test plan for the application. This helps in performing testing in a flow.
  2. Design the test cases considering all the possible scenarios and end cases.
  3. Identify critical modules to be tested on priority. It is essential to understand the application’s architecture design.
  4. Demonstrate the test conditions for each unit. Once the requirements are listed, these must be documented to use further while performing tests.
  5. Run the test cases after integration.
  6. Detecting and fixing errors.
  7. Retest the functionalities after fixing the errors.
  8. Repeat the process until all the errors are found and fixed.

Integration Testing Tools

  1. Protractor: This is an open-source framework. It is preferred for applications based on angular and angularJS. This tool is specially used in integration testing. It helps to run application instances. It helps in running tests from the user's point of view.
  2. Rational Integration Tester: This tool helps in providing a scripting-free environment and helps in avoiding bugs and reducing test cycle time as this testing is performed at an early stage. It provides features such as creating code-free and reusable stubs. It also reduces the risks of failure.
  3. Tessy: This tool performs integration and unit testing for embedded systems. Testers can easily specify the test cases. This tool also helps generate test reports for the execution results and identify the application’s code coverage. It supports C and C++ programming languages.
  4. LDRA: It stands for Liverpool Data Research Associates. This tool helps in automating the code analysis for testing. It is an open-source tool that helps build integration tests and provide dynamic analysis. 

Advantages Of Integration Testing

  • This testing ensures that the integrated components work properly.
  • Integration testing doesn’t require all the other modules to be available. It can be done right after acquiring the module that needs to be tested.
  • It detects the errors related to the interface.
  • It helps in improving the overall performance of the application.


  1. What is a Latent Defect?
    The latent defect is an existing defect in the system that does not lead to an error since the same set of conditions are never fulfilled.
  2. Describe the functions of a software testing tool “phantom”?
    “Phantom” is a freeware used for GUI automation scripting language. It allows taking control of the functions automatically. It can simulate random combinations of mouse clicks, keystrokes, and more.
  3. What is Fault Masking?
    When the presence of one defect nullifies the effect of another defect in the system, it is known as fault masking.
  4. State the difference between the Trace Matrix and Traceability Matrix?
    The Test Matrix captures the original quality, plan, effort, and time required to capture all phases of testing, whereas the Traceability Matrix is a document used to map the relationship between the test cases and the customer requirements.

Key Takeaways

In this article, we have extensively discussed Integration Testing. The main aim of Integration Testing is to test the interface between different components and expose any defect that may arise due to the integration of the components. Testing is a crucial part of the development process and needs to be done thoughtfully. 

We hope that this blog has helped you enhance your knowledge regarding Integration Testing, and if you would like to learn more, you can follow our guided path. Do upvote our blog to help other ninjas grow. 

Happy Coding!

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