What is Integration Testing?

Integration testing is a type of software testing in which software components are gradually integrated and then tested as a unified group. These parts typically function well independently, but they could malfunction when combined with other parts. When software modules are integrated, code conflicts can lead to defects. This is why integration testing is done.

Software module conflicts can occur for various reasons, including incompatibility between subsystem versions, data format inconsistencies, or processing logic disparities. Integration testing identifies these communication problems between software components. It usually happens before system testing and following unit testing.


Why is Integration Testing Important?

Software module conflicts can occur for various reasons, including incompatibility between subsystem versions, data format inconsistencies, or processing logic disparities. Integration testing identifies these communication problems between software components. It usually happens before system testing and following unit testing.

Inconsistent code logic: The modules’ disparate authors’ differing approaches to development and logic make them difficult to integrate and may result in usability or functional problems. Integration testing produces an application that functions by ensuring that the code underlying these elements is in sync.

Requirements changing: Customers often have different needs. Sometimes, modifying one module’s code to accommodate new requirements necessitates completely altering the module’s code logic, which impacts the entire application. Because unit testing may only sometimes capture these changes, integration testing is necessary to find the flaws that are being missed. 

Erroneous Data: When data is moved between modules, it can become inaccurate. When data is transferred improperly, it cannot be read or processed, which leads to bugs. Integration testing is necessary to identify the problem’s location for troubleshooting purposes.

API integrations and third-party services: Since data can change during transmission, these services risk receiving erroneous input and producing erroneous results. Integration testing ensures that these integrations communicate well.

Inadequate exception handling: Although developers typically consider exceptions when writing code, there are situations when this isn’t possible until modules are assembled. Thanks to integration testing, they can identify absent exception scenarios and make changes.

External Hardware Interfaces: Software-hardware incompatibility is another common cause of bugs, and it is quickly discovered through appropriate integration testing.

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Types of Integration Testing

There are various methods for carrying out integration testing, each with pros and cons. The two most popular methods are as follows:

  • Big Bang Approach
  • Incremental Approach

Three different methods carry out the Incremental Approach:

  • Bottom-up approach
  • Top-down approach
  • Sandwich approach

Big Bang Approach

An approach to integration testing is to integrate and test each module individually, all at once, as a single unit. The integration process is not initiated until every component has undergone successful unit testing.


  • Ideal for small, straightforward systems with minimal software component dependency
  • Minimal to no prior planning is necessary.
  • Due to the simultaneous integration of all modules, setup is simple.
  • Management and coordination efforts are minimized because there is only one significant testing phase.


  • It is costly and time-consuming for extensive systems with lots of units because testers must wait to begin testing until every module has been created.
  • Defect detection occurs later when testing is delayed until all modules have been developed.
  • Difficult to identify and isolate errors in particular modules
  • It is a challenge to debug because of the intricacy of several integrated modules.

Incremental Integration Testing

An approach known as incremental integration testing involves testing two or more modules with logic and functionality that are closely related to one another before progressively moving on to other groups of modules. This eliminates the need to test every module at once. Once every module has been tested and integrated, the process is over. Compared to Big Bang testing, incremental integration testing is more strategic and necessitates extensive planning in advance.


  • Earlier defect detection because modules are integrated and tested as soon as they are developed, unlike Big Bang testing. Testing can start as soon as all modules are available to QA teams.
  • Because the modules are tested in relatively small groups, fault localization is made easier.
  • Project managers can benefit from incremental integration testing’s strategic nature. QA managers have the option to select the module to test first based on factors such as resource availability, urgency, or priority.
  • Since the root of the problem is addressed early on, the risk of catastrophic failures is also significantly reduced.


  • Require careful preparation in advance.
  • Depending on the size of the project, there may be many tests to complete, necessitating a substantial amount of organizational resources.
  • Using this method to organize a big integration testing project could be challenging.
  • Before the system is divided into smaller parts, the system must have a clear definition and logic.
  • Early in the project, it’s possible that some system functionalities won’t be available, forcing you to rely on stubs and drivers—basically, mock components that will be used in place of real ones.
  • If early system functionalities are not thoroughly documented, they could result in system “blindspots” later.

There are three smaller subcategories of incremental integration testing, and each has pros and cons that QA teams should carefully weigh before implementing a project. The following approaches are named according to the degree of influence that the software components undergoing integration have on the system as a whole:

  • Bottom-up approach: start with low-level components and work your way up to higher-level ones.
  • Top-down approach: start with high-level components and work your way down to lower-level ones.
  • Hybrid approach: merging the two previous strategies

Read More: DevOps Automation, What is DevOps and how it helps to automate software process.

Examples of Integration Testing Test Cases

Integration testing is the process of attempting to determine how two or more entities interact. It can be used to observe how two service classes communicate, how a service communicates with a data store, and how the user interface reacts to the backend.

  • Verifying the interface connection between the Login and Get Started pages. The system is supposed to confirm that a user’s credentials are correct after they are entered, and if they are, the user will be taken to the Get Started page as a logged-in user.
  • Verifying that the appropriate data is sent in the proper format to the appropriate location when a user fills out a form
  • Verify that the order history and confirmation emails accurately reflect any changes made to the user profile.
  • Verify that products are restocked after being marked as out of stock when their inventory falls to zero.
  • Verify that users receive accurate shipping information and that tracking updates are displayed as intended.
  • Verify that the chosen items are placed into the shopping cart appropriately and that the order is completed successfully, updating the inventory and producing an order confirmation.

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Integration Testing Best Practices

Testers need to align with developers and clients on their vision and optimize their strategy along the way to have a comprehensive integration test strategy covering every aspect of the application. It is imperative to adhere to best practices for integration testing in any case:

  • Before beginning the integration phase, ensure that every module has undergone unit testing to ensure the validity of the integration test results.
  • Develop a thorough test strategy and plan that details the resources, goals, test cases, and scope needed for integration testing.
  • Automate repetitive and complex test cases to increase testing efficiency and preserve test consistency between runs. Discover the best method for performing automation testing here.
  • To increase test reliability, validate the input test data.
  • After every integration, conduct regression testing to ensure that the new modifications don’t negatively affect the previously integrated components.

Manual Testing vs Automated Testing

Manual integration testing can be performed by QA teams, typically in parallel with the development process.

The process usually begins with the development team committing new code to a shared repository, followed by a series of unit tests to validate the new code. Then, QA testers select different components based on the test plan to manually inspect and interact with, checking for defects.

However, doing integration testing manually is only sometimes the best option. 

Automated integration testing, whether using automation frameworks such as Selenium or automation testing tools, can significantly accelerate the process and free up resources for other tasks.


Integration testing is an integral part of software testing because it determines whether the modules can communicate effectively with one another, which unit testing cannot do. We can use either the Big Bang or the Incremental approach to integration testing, each with advantages and disadvantages.  

API and UI Integration Testing are common types of integration testing. However, professionals may need help to perform those tests in a single location and must constantly switch from one tool to another when performing different testing types.

Frequently Asked Question

The types of Integration Testing are: 

  • Big Bang Approach
  • Incremental Integration Testing
  • Top-down Incremental Integration Testing
  • Bottom-up incremental Integration testing
  • Hybrid Approach

API testing is actually system integration testing (also known as interface testing). When performing integration testing, the two systems will most likely require an API to connect and communicate with one another. An API is a standardised way for systems to interact with one another.

Citrus. Citrus is a popular integration testing tool that is commonly used in software development projects. It provides a framework for testing the interactions of a system’s various components, such as web services, messaging systems, and databases.

An integration test is a type of functional testing that looks at how various modules interact with each other. PractiTest test management platform could greatly assist you in managing all types of functional and non-functional testing.

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