Integration Testing: What is it, Types and Examples


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Building intricate and interrelated applications has become standard in the ever-changing software development landscape. As technological innovations and consumer demands rise, flawless integration of multiple elements has become a key indicator of software success.

Testing is essential for ensuring software systems' seamless operation and dependability. Performing testing early in the development process can help identify and fix issues. This saves precious time, money, and effort in the subsequent phases of development.

Integration Testing

Developers can deliver robust software that meets the user’s needs with the help of system integration testing. However, a question arises: What is integration testing? How can it be performed, and what are its types? To answer this, let’s delve deeper into this topic. This blog will also explore the unit test vs integration test and integration testing examples. So, let’s get started.

What Is Integration Testing

This type of testing examines how various software application modules interact and operate cohesively. The program is divided into more components, known as modules or units. Each module is responsible for a specific task. The real challenge comes when we combine these components to develop the entire software system. 

At this stage, it begins to carefully examine the connections between each module to discover any possible problems resulting from a single unit. When the testing is complete, end-to-end testing is conducted to assess the application’s functionality from start to finish. It considers the whole user journey from the initial to the final output to identify issues when various units interact. 

Software modules are manually combined, and their relationships are evaluated in manual component testing. Manual testing can be laborious and vulnerable to human error. It can be challenging to cover all integration possibilities in complicated systems adequately. To address these issues, automation is frequently employed. 

Continuous integration and continuous delivery practices can aid in this automation. CI/CD pipelines automate the code’s development, testing, and deployment. CI/CD tools automatically run integration tests to verify that the new code integrates well with the existing system. It makes it simpler to address issues before they become more severe by enabling immediate input to developers.

Like other testing procedures, system integration testing involves performing a series of steps to create a flawless application. Here are some vital pointers to note:

  • Creating a testing plan: The testing plan includes the objectives, scope, and approach of the testing phase. This helps testers and stakeholders to understand how the testing will take place. 
  • Begin with essential modules: Prioritize the most vital modules when developing test cases. These components are likely to trigger issues if they are not adequately integrated.
  • Use various tools: Numerous tools are available for implementing and running integration tests. Select the tools that best meet your requirements and financial constraints.
  • Perform the tests in various settings: This will ensure that the tests are solid and capture any flaws in multiple environments.
  • Evaluate the results thoroughly: This is a crucial phase in the testing procedure. You can discover any flaws that require repair by carefully evaluating the findings.

Unit Test vs Integration Test

Unit and integration tests serve distinct purposes and are carried out at various development lifecycle phases. The following table compares the key distinctions between unit tests and integration tests:

Aspect Unit Test Integration Test
Scope Concentrate on particular units or modules. Examine the interactions of integrated modules.
Purpose Check that each item functions independently. Check that all the interconnected pieces work correctly.
Isolation External dependencies are kept separate from the tests. Integration with real-world modules is required.
Speed Because it focuses on small units, execution is quicker. The execution time for is a bit longer due to the testing of various modules.
Coverage Offers extensive code coverage by exhaustively inspecting particular modules. Ensures that modules perform correctly as an element of the overall system.
Testing Workflow The developers typically perform unit tests before the integration. Integration tests are usually performed during the integration phase of the Software. 

Integration Testing Types

Integration testing types


It can be divided into two subtypes:

  • Incremental testing
  • Non-Incremental testing

Incremental testing involves testing software modules in small increments. The testing of the software starts with smaller pieces and works its way up to the entire system. 

Each test improves the software by integrating additional modules. Compared to testing the complete system simultaneously, this offers advantages, including early feedback, more straightforward troubleshooting, and decreased complexity. Incremental testing provides two main types:

  • Top-Down integration 
  • Bottom-Up integration

Non-incremental testing involves testing software modules. In this type, the testing takes place after all the modules are developed and ready for integration. The whole software is tested at one time. The non-incremental testing is often known as the big bang integration approach for testing. Let’s look at how these types work and what advantages they offer.

  1. Top-Down Integration 

Top-down testing employs a systematic approach to testing the software modules from the top level down through the system hierarchy. The testing begins with the main module of the software and then proceeds to test the submodules of the application.

Its primary goal is to ensure functionality between the higher-level modules and their submodules. As the testing procedure progresses through the hierarchy, module relationships are checked to ensure the software components operate as designed.

top down integration testing

Since higher-level modules undergo evaluation before lower-level ones, this technique enables the early discovery of high-level design faults. It aids in the early development phase’s detection of potential structural issues.

Stubs can emulate lower-level modules, so testing can start even before they are entirely constructed. This aid in improving the testing procedure and give the development team input more quickly.

  1. Bottom-Up Integration

When performing Bottom-Up testing, lower-level modules are tested first. It gradually moves to the higher-level modules, and so on, until all facets of the software have been thoroughly tested. This strategy is referred to as inductive reasoning. It is beneficial when incorporating pre-made or already-existing components into the final product.

Bottom up integration testing

It involves writing code for various modules rather than focusing on stubs or mock objects. That’s why its success rate is higher than other approaches.

Furthermore, the execution time for the tests is frequently shorter than other traditional methodologies. This makes it simpler for the testers to conduct tests and construct the project to achieve the best results possible.

  1. Big-Bang Approach

It entails compiling all software modules into one structure and evaluating it as one unit. Individual modules are not examined separately. Instead, they are combined and tested in a single process. 

It necessitates firm communication between the development and testing teams to appropriately identify and solve any issues detected during the testing procedure. The big-bang strategy can be quicker and less expensive than alternative approaches, as developers don’t need incremental testing.

This strategy could work for software systems with fewer and less intricate component relationships. However, it might be challenging to identify the precise module when flaws are discovered during testing. Let’s check out the integration testing example to see how it works.

Example of how to do Integration Testing


The web application for booking flights is designed to provide a hassle-free booking experience. The System Under Test (SUT) comprises various modules. Each module serves a specific role to provide a flawless user experience. 

The primary module functions as a user interface, making it easier for users to engage with the application. The interface lets users enter their travel preferences, including date, destination, departure cities, and passenger details.

The searching flight module processes the primary module user input. It searches a flight database or other APIs for available flights that meet the criteria supplied. The module then presents the search findings, which include flight choices, schedules, airlines, and pricing.

The payment module manages the safe and effective processing of payments for the chosen flights. After the user has finished the payment procedure, the confirmation module creates a booking confirmation. This confirmation contains booking references, passenger names, and other crucial details. It can be sent to the user or printed.

Top-Down Approach Example

The top-down testing starts by validating the primary module separately. It means the primary module is tested independently from the subordinate modules without integration.

The lower modules are then integrated and tested one at a time once the main module has passed each of its independent tests. The flight search module is first integrated and tested with the primary module. The payment module is then integrated, tested, and finally, the confirmation module. The process continues until all of the units are integrated and tested.

Bottom-Up Approach Example

The flight search, payment, and confirmation modules are unit tested, ensuring they work as intended. First, the payment and search flight modules are combined and tested. This test verifies that customers can correctly complete all aspects of the booking procedure, including searching for flights and making payments.

Then, search flight and confirmation modules are combined to ensure that consumers receive confirmations of bookings after finishing the payment procedure. The process continues until all the modules are tested.

Big-Bang Approach Example

All modules, including primary, flight search, payment, and confirmation, are combined into a single system under the Big-Bang technique. Several test cases are carried out to evaluate how well the system functions, interacts, and performs.

Advantages of Integration Testing

While performing tests for integration, it examines how the complete software program serves as a unit, just as it will when people use it. The context-driven approach entails examining the precise setting in which the product will be used. It recognizes that the software’s operation depends on more than just its components. 

It also depends on how these components interact when seen as a whole. It’s similar to considering how a team functions rather than just each player’s skills.


Integration testing advantages

1. Validate Dataflow

It examines how data moves between various units and database servers. It validates that data is transmitted effectively and without degradation. This reduces the danger of data-related issues in the live environment.

2. Identifying External Dependencies

Most software programs utilize external resources like APIs or third-party systems. It examines how the software interacts with these dependencies through real-world simulation. This aid in the identification of any compatibility issues.

3. Customized Test Scenarios

It enables testers to develop specialized test scenarios that reflect the software’s unique properties and user interfaces. This allows a more accurate assessment of critical features.

4. Scalability Validation

It validates scalability by using a context-driven methodology. This looks at how interconnected units manage rising workloads to ensure the system can support expansion in the future.


As technology advances, users require applications to deliver excellent efficiency, protection, and dependability. Testing various modules while integrating is an important quality assurance strategy during the software development lifecycle. 

It encourages engagement and cohesiveness among diverse software modules. Developers can improve their workflow by detecting and fixing integration-related errors early in development. It can aid in lowering the time and resources spent on problem repair in later phases.

When, combined with other testing methodologies such as unit, functional, and end-to-end testing, it aids in developing a comprehensive testing strategy. This technique guarantees that the finished product matches or even surpasses user expectations. This increases consumer happiness and retention.