Testing is integral to software development. Before launching any web or mobile application, companies must ensure that all systems work as intended.

Businesses can continually update their software and correct bugs. However, doing things right the first time can save them a lot of money.

Buggy or malfunctioning software systems not only affect internal operations but also affect how clients see your company. Bugs cost time and money to fix, not to mention the risks they pose to your reputation and customer base.

Software testing involves different methods to ensure your application works well overall. This post will explore System Integration Testing, a vital part of the testing process.

Key Takeaways

• System Integration Testing is necessary to ensure the system works before it is released or used.
• There are several approaches to testing systems.
• Some methods are more laborious, time-consuming, or result in a loss of control.

System Integration Testing Defined

Software projects and applications often involve multiple software modules created by different programmers. A system must be in place to ensure that each unit or module works well with one another.

System Integration Testing, also known as SIT, is a type of testing that involves the entire system infrastructure. It helps ensure that all systems or subsystems work according to standards. It is a step above unit testing and occurs after each smaller subsystem or module passes its tests.

SIT combines and tests at least two systems or subsystems as a whole. It can involve tests between two or more software, hardware, or software-hardware components. SIT guarantees proper data flow and integrity between the different modules.

The entire system doesn’t have to be tested all at once. Some modules may be tested separately before integrating them with others. In these cases, SIT tests the interaction between these smaller systems and confirms whether they pass the set requirements.

The process could start with one module, and hardware or software modules are added individually. Testing them as you go helps you build a working base and identify problems immediately.

Why Do You Need System Integration Testing?

System Integration Testing is necessary for quality assurance. Skipping it could leave your final software product with significant problems.

Before releasing any software for use, you need to ensure that the project’s components flow seamlessly with one another. Below are some areas and instances that best showcase the necessity of SIT.

Save time and resources

SIT allows you to identify possible mistakes and make the necessary changes and fixes as soon as possible. Promptly addressing defects helps you save time and resources compared to fixing them later. Waiting until after users submit complaints takes more time. It can also take resources away from other projects you might need to prioritize.

Address changing software requirements

Aside from saving resources, SIT allows you to address changing software requirements. No software project is perfect, and prior planning issues could influence future functionality and implementation.

Managers could change their minds about what they want the software to do. It is often easier to change things early on in the process rather than later.

However, changes could come unexpectedly. Programmers then need to be able to make adjustments as they pop up. Common reasons for changing requirements include:

• Developer error in meeting requirements
• Defects in the initial design
• Insufficient resources
• Changes in marketing strategy
• Changes in competitor response
• Staffing changes, such as stakeholder withdrawals and turnover errors
• New ideas or available technologies for improvement

Add new features

For an application to run smoothly, each software module needs to be able to communicate and work seamlessly together. Changing or adding features introduces new components to the overall project. Even with more minor changes, you will still require testing to ensure the new code doesn’t create disruptions.

New features consist of multiple units and modules that have not yet been tested against the overall system. They might work well independently but could cause problems as they interact with the rest of the application.

SIT allows you to determine whether your existing software system accepts the added modules or features. Even minor changes require rigorous testing to ensure no new issues pop up.

Types of System Integration Testing

Quality assurance and development teams can perform System Integration Testing in a few different ways. You can explore these different approaches and see which methodology works best for your specific project requirements.

Top-down method

As the name suggests, the top-down or top-to-bottom SIT method starts with the app’s main functionality or module. Each submodule is then added in order and tested to see whether they are well-integrated.

In some instances, some submodules may still not be ready. These cases call for the use of stubs or called programs. They act as dummy modules and partially perform the functions of the required submodule until it is ready.

Once all submodules are ready, developers replace the stubs, and the models get tested accordingly. This process continues until all modules are complete and tested.

Some teams may prefer the top-down approach for the following reasons:

• Modules undergo tests in order of importance.
• It is easy to detect malfunctions and their origins.
• It takes less time than other system integration methods.

However, the top-down approach may not work for all projects. This is especially true if the lower-level modules contain information necessary for the system to work. The rest of the project might experience delays with this method.

Bottom-up method

Like the top-down method, this approach involves incremental module testing. However, bottom-up testing begins from the lowest modules, and you work your way up.

First, the lowest modules or units are merged into clusters and then tested. You could create multiple clusters to combine related modules.

If the primary or topmost module is not yet ready, you can use a placeholder, like in the top-down approach. Drivers, or calling programs, could be used in these cases.

One key advantage of the bottom-up approach is that you can apply it even in the early stages of development. You can test the integration of smaller units until you finish the main module and integrate the whole system.

However, this approach could be time-consuming, especially for projects with many low-level units. You cannot release your software product until you complete all low-level modules and integrate them with the main one.

Sandwich or hybrid method

Sandwich testing, or the hybrid method, combines the top-down and bottom-up approaches.

Top-down and bottom-up techniques are performed simultaneously before combining them. The topmost module (like the user interface) gets tested using stubs. The lowest modules are merged into clusters and tested using drivers.

Testers integrate and test upper and lower-level modules once these steps are successful.

The sandwich testing strategy is best suited for larger projects composed of several modules. Below are some of its main advantages:

• It allows parallel or simultaneous testing.
• It saves time.
• It allows for more testing coverage.

However, the sandwich approach might not be best for every project. It could be costly, especially as it involves multiple simultaneous levels of testing. It could also be tricky to navigate projects with many dependencies between modules.

Big bang method

In the big bang approach, all modules across different levels are tested and integrated simultaneously. Once your team completes all codes and modules, you can test the complete system in one go. There are no partitions or placeholders.

This method’s most significant advantage is that it is one of the quickest and most cost-effective testing methods available. If successful, you only need to perform one round of testing.

However, this advantage only applies if the modules and test cases have no errors. Otherwise, you will need to split the project into smaller units to find the defect, which can be time-consuming.

The big bang method is best suited for smaller and simpler software projects. Spotting errors are easier to do with fewer modules and subsystems.

Pro Tip

Incremental testing is an approach to integration testing conducted whenever you add a new unit or module to the system. It is time-consuming, encourages more frequent tests, and makes early detection of issues more manageable.

Keep Your Systems Efficient With Help From Brain Box Labs

System Integration Testing is a critical part of the software testing process. It ensures the quality and functionality of your software project.

A well-integrated system minimizes errors and improves user experience.

The entire testing process could be overwhelming, especially if it involves several moving parts. You can consult application developers from Brain Box Labs to help create test plans that work best for your project.

Ensure your systems work seamlessly together with System Integration Testing services. Contact us today if you have any questions or want to schedule testing sessions with our development team.