This article discusses the importance of integration testing, as well as its purpose, types, and advantages.

What is integration testing?

Any piece of software is made up of various modules that execute various tasks. Although a software module may work well on its own, Integration Testing ensures that the software works effectively when all modules are combined.

Integration testing assesses the functionality of many modules when they are combined into a single unit. This testing ensures that the software’s numerous interconnected components work together smoothly. The goal of integration testing is to uncover flaws and vulnerabilities in the software’s many interfaces.

Why do we need integration testing?

Integration testing is required for the following reasons:

  • Defects in interconnected modules are difficult to discover and difficult to correct.
  • Fixing faults in integrated modules can reduce the amount of code changes at the next level of system testing by reducing the overall number of bugs.
  • Integration testing allows us to assess the integration of multiple software components, which aids in the evaluation of the product’s end-to-end cycle.
  • This method of testing also lowers the chances of software failure.
  • It also verifies the impact of structural modifications as the user progresses from one module to the next.
  • It aids in the verification of the software’s third-party API tools’ accurate functionality.
  • Error trapping, hardware interfaces, data formatting, and third-party interfaces are among the difficulties that were overlooked during unit testing. Integration testing also examines the integrated interfaces’ functional and non-functional behavior.
What are the benefits of integration testing?

The testing method has a number of advantages, including:

  • Integration testing ensures that the modules and their outputs are suitable.
  • It also aids in the detection of problems with module interfaces.
  • Integration testing encourages the interaction of different elements.
  • It covers a variety of modules in order to provide more comprehensive test coverage.
  • Integration testing has an impact on the software’s overall testing efficiency.
  • It aids in the seamless transition between interfaces.
How to approach integration testing?

Integration testing involves combining several functional components and then testing them to see what happens.

Incremental testing approach

This type of integration testing is done on a unit of logically connected modules.

All modules are added to the testing unit one by one until the testers have covered the complete system. Because some modules are still in development, incremental testing frequently employs stubs and drivers. Stubs and drivers are dummy programs that help create communication but do not implement logic.

This approach has three approaches to select modules:

Top-down testing

Top-down integration testing involves testing from the top down, in accordance with the architectural structure or control flow.

The top-down approach allows testers to evaluate the first top module in isolation before adding further modules to the testing unit one by one as they progress below. In this approach, testing control flows from top to bottom in the system. Because the lesser modules may still be in development, testers employ stubs as dummy programs that provide control back to the superior modules.

The following are some of the advantages of this strategy:

  • Locating a fault is simple.
  • Designing a prototype quickly
  • Prioritizing the most important modules
  • Finding and fixing design issues is simple and rapid.

The sole disadvantage of this method is that lower-level modules in development are not tested.

Bottom-up testing

This approach tests the lowest module first in the architectural structure. The other modules are incrementally added one by one for testing moving upwards in the architectural structure. The control of flow in testing moves from bottom to upwards.

This testing method is implemented when the top modules are under construction. The method uses drivers to stimulate the functioning of missing modules. The drivers perform various tasks such as calling module under test, passing test data, or receiving output data.

  • Easy to test and develop the product
  • Efficient approach for integration testing
  • Easy to create test conditions
Sandwich approach

The sandwich approach comprises testing the software’s architectural structure’s bottom and top modules.

The middle layer (layer2) is the aim in this strategy, and the tester must reach it. To begin testing, the entire software system is divided into three layers.

The middle layer is the first, the layer above it is the second, and the layer below it is the third. A tester’s purpose is to test both levels simultaneously in order to reach the intermediate layer.

Big Bang integration 

This method of integration testing begins once all of the modules have been completed. All of the units are put through their paces as a single unit. Smaller systems benefit from this type of integration testing. There are certain restrictions to big bang integration, for example:

Finding translation issues that cause testing to be delayed is difficult.

This strategy also makes it harder to pinpoint the source of a problem.

Because all of the interfaces are checked at the same time, the testing team must devote more time and effort.

Critical modules are not prioritized, potentially putting the entire system at danger.

What are the steps to integration testing? 

The steps of integration testing are as follows:

  • Understanding the application’s architecture is the first step in performing integration testing.
  • Locating the system’s numerous modules.
  • Each module’s functionality should be understood.
  • Examine the data exchange between interfaces.
  • Examine the system’s entry and exit points.
  • Prepare a testing strategy.
  • Choose a testing strategy.
  • Sort the modules into categories based on how they’ll be tested.
  • For each test scenario, identify the various test conditions.
  • Create scenarios, scripts, and test cases for your tests.
  • Deploy the modules you’ve chosen and test their integration.
  • Carry out the test cases.
  • Keep track of the flaws and keep track of the consequences.
Continuous integration

This type of integration testing focuses on delivering speedy releases by decreasing the amount of time it takes to detect and repair bugs. Continuous Integration takes an architecture-based approach, giving development teams additional flexibility.

An integrated code is shared to the main branch of the repository to generate a build in this type of integration testing. The build is automated checked to avoid regression bugs after integration, allowing for a speedy release. When a new integration is established, this testing aids in determining the system’s stability.


Integration testing is essential to create a system that is reliable and behaves as planned. This type of testing assures that individual units are compatible with one another.

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