What is Integration Testing? A Complete Beginner's Guide

Before releasing software in the market, it is thoroughly tested for its functioning, features, and proper working. The released software will not be influential to your customers without conducting proper testing. The softwares need to be tested, and one of the essential testings is integration testing which is a part of the functional testing process where the teams test for the software in its development phase. Functional testing ensures the quality of the software by providing input and analyzing the outcomes. Different types of functional testing are used to ensure the overall performance of the software or system. These tests highlight potential errors, evaluate the systems, analyze their behavior and performance. Most organizations conduct unit and functional testing to ensure the software’s proper development. Thus, companies must put enough effort, time, and money into testing real test cases that are usually ignored. Apart from this, most organizations only execute integration testing that guarantees fast and accurate software development. Different testing has different requirements to conduct the test successfully and aims and ways to ensure the software’s proper working. We have focused on integration testing, how it is different from the unit and system testing, why we need to implement integration testing, different types, its benefits, its challenges, how to adopt integration testing, and various tools to do integration testing.

What Is Integration Testing?

The meaning of integration testing is simple, and it means combining different modules of unit testing and then testing them as a single unit to understand their behavior. Integration testing helps test the interfaces among various modules, if they can interact seamlessly, without impacting the software’s working. Integration testing allows the team to test whether all the requirements are implemented per the client’s requirement. Integration testing mainly occurs after the unit testing, when you ensure the proper functioning of all your modules. First, each module is tested separately and integrated to check their combinational behavior. Also, you need to understand that integration testing does not occur at the end of the development cycle. You need to conduct integration testing continuously throughout the development phase. In the development phase, all your single modules are not ready to test their combined effect, and this is where the actual challenge occurs during integration testing. Generally, the team conducts integration testing using a black-box method. The testing team interacts with the application and its various modules using the user interface to provide the input. You will get the outcome of the provided input, which the team will analyze to understand if the application is working as expected. Other testing methods are equally important, such as unit and system testing. But before you implement integration testing, you must understand how it differs from both.

Differences Between Integration and Unit Testing

Software testing has various levels of testing under it, and two of them are unit testing and integration testing. The unit testing occurs before the integration testing, as testing an individual module is the first thing to do. Unit testing ensures the testing of the smallest units of code separately under different settings, while Integration testing helps determine the errors after combining those modules. If the individual modules are working as expected, there is no guarantee that they will work when combined to provide expected results as many factors can result in deviated outcomes. Some errors can be due to the interaction between these units; thus, integration testing is necessary.

Difference Between Integration and System Testing

Integration TestingSystem TestingIndividual units are combined and tested.It tests the software application as a whole.It checks for the integrated module’s functionality, reliability, and performance.It ensures the compliance of the developed product as per the user’s requirements.You can implement it as white-box testing and black-box testing.It is a black-box testing technique. Thus, technical knowledge is not required.It looks for potential faults in the interaction between integrated units.It looks for functional and non-functional attributes of the software.Testing engineers and software developers conduct this testing.Testing engineers conduct this testing.It is performed after unit testing.It is conducted after the process of integration testing.

Why Do We Need Integration Testing?

Irrespective of how well-written the code is, it may work unexpectedly. Any software module can work well individually, but we also need to check if the integrated module is also working as expected. We need the complete software in fully functioning condition. Thus, integration testing must be conducted to ensure the efficiency and working of the software. Below are some reasons you should run integration testing once you are done with single testing modules.

• It is challenging to determine and fix bugs in integrated components. Conducting the thoroughly tested units eliminates potential errors at the earlier stage of development.

• Integration testing is faster than running end-to-end tests.

• You can do integration testing to find system issues, such as cache integration, corrupted database schema, etc.

• Integration Testing reduces the chances of software failure to a great extent.

• It lets you check the structural changes whenever a user moves from one module to the next.

• Integrated testing reduces the bugs in the entire system and enhances overall performance.

• You can seamlessly cover multiple modules and open broader testing capabilities.

• Some modules are designed to interact with third-party tools or APIs and require testing to check if the data accepted by that API / tool is accurate and generates the expected response.

Benefits of Integration Testing

Integration testing breaks down the complex and multi-level code into smaller blocks consisting of several thoroughly tested units before you combine them into a complete system. It ensures that the entire system is under consideration again, regardless of when, how, and why they were created. Checking and validating the software’s integrity is crucial; it will be challenging and time-consuming to determine potential bugs. Here are some benefits of implementing integration testing.

• Integration testing allows the testing of different modules simultaneously, making it more convenient, practical, and cost-efficient.

• Integration testing occurs at any stage of the SDLC, eliminating the effort to make considerable changes in the code later at the development phase.

• It works well for teams involved in projects with constantly changing requirements or logic, as you need to test integrated modules repeatedly after making the changes.

• Unlike another testing process, integration can cover huge program code in a single sprint.

Types of Integration Testing

You can conduct Integration testing in various ways to ease your testing process. Different testers have different approaches to conducting integration testing as per their requirement. There are five different approaches to do integration testing. We have mentioned them below with their pros and cons. It will help you understand which approach works well to make concrete decisions.

• Bottom-to-Top Testing

This testing starts from the lowest level of the software you want to test. The QA engineers move upwards to test each module in the hierarchy. The testers go from bottom to top to test the already prepared units. Pros of a bottom-up approach

• You can develop individual modules while running integration tests, and you can use this approach.

• In case of errors, you can fix them at the same level without migrating them to the next level. It ensures easy identification and fixation of errors.

• This approach takes less time to correct the error.

Cons of button-up approach

• This approach will take more time as you need to continue till all the modules are tested. Thus, overall testing time is more.

• Also, if the software has several modules, it will take more time.

• Drivers have to call the high-level modules while testing the bottom-level modules.

• Top-to-Bottom Testing

It is the opposite of the bottom-up approach. In this case, the testing process starts with the top-level modules and gradually moves to the lower levels. In some scenarios, there might be chances that some modules are not ready, then you use stubs – units acting as a temporary replacement. You will get the same outcomes using the stubs as you will get in the case of an actual product. You can implement this testing even if elements are missing. Pros of top-to-bottom approach

• It makes the detection of errors much more accessible.

• It allows you to test the priority modules first then move to the low-level modules.

Cons of top-to-bottom approach

• If the base logic is integrated within the lower-level units, you cannot test it before testing the other upper-level modules.

• You need to use stubs for almost every testing that might provide an expected outcome.

• Big Bang Testing

A QA engineer will test if all the modules are combined into a single system. In this case, integration testing will start when you write the base code, and the first version of your software is ready for release. This approach will save your time as a team will not stop the development process to test every unit. Make sure that the test cases are flawless, and else you have to break down the code again to start over with the testing process. Pros of the big bang approach

• You can use this approach for testing small systems.

• It helps determine early-stage bugs, saving a lot of time and effort.

Cons of the big-bang approach

• It might be challenging to find the source of the error as it includes the testing of the entire system.

• Reviewing each unit will consume time to test a complex system with many units.

• Hybrid/Sandwich Testing

This approach combines the benefits of both bottom-up and top-to-bottom approaches. The goal is to reach the mid-module by simultaneously testing top and bottom modules. In the case of the hybrid model, you need to test the top units separately, and low-level units are tested after the integration with upper-level units. You have to use both stubs and drivers in this approach. Pros of the hybrid approach

• You can use this approach for large projects.

Cons of the hybrid approach

• This integration testing approach will incur more cost as units at different levels need simultaneous testing.

• Incremental Testing

A QA team starts testing the integrated units once the development team completes the code writing for every new feature. This approach requires more frequent checkups. It means that whenever a new feature is added to the system, you need to pass its complete check. Pros of the Incremental approach

• Testers can quickly determine the potential defects early and in smaller assemblies, reducing the cost of a mistake.

• Due to its step-by-step examination, finding errors becomes easier.

Cons of the incremental approach

• You need to create stubs for tests and thus require more testing time.

After considering all the integration testing approaches and their pros and cons, you can easily decide which approach to use for your project. It might be possible that you have to implement more than one approach to your project, so decide smartly to reduce your time and effort.

How to Adopt Integration Testing?

Every testing comes with some standard procedure to implement. Here are the steps that you can follow. If you successfully implement the steps, there are high chances of getting high-quality software in a single go. But it is up to your project requirement, and you can alter the procedure if required.

• Understand the underlying architecture of an application.

• Identify what and how many modules are present in an application.

• Analyze the detailed functioning of individual modules.

• Understand the data flow among all the modules.

• Understand how you input the data and get the outcome.

• Based on the above knowledge, create test cases.

• Consider a single condition at a time while writing test cases.

• Before you test, make sure to identify the exit and entry criteria of the application.

Entry Criteria

You need to ensure the following conditions are satisfied before your test.

• Unit testing of each module.

• All the high-priority bugs need to be fixed.

• All the modules are integrated successfully.

• Prepare test cases and test plans.

• Set up an integration testing environment.

Exit Criteria

Make sure the following conditions are satisfied after the integration testing.

• Successful Testing as expected.

• All executed test cases are perfectly and thoroughly documented.

• High priority bugs fixed and closed with proper steps involved.

• Submit technical documents along with a release document.

Challenges of Integration Testing

Nothing is perfect and comes with challenges. The same goes for integration testing. As most of the work is manual and requires proper knowledge to conduct integration testing, there are fair chances that you will face several challenges. We have mentioned some of the commonly occurred challenges that might differ from yours. But, you can also consider the below for better understanding.

• If you have a big project that might involve various developers with different code writing patterns. It makes it challenging to understand the logic of another developer.

• Sometimes having too many factors such as database, platform, settings, servers, etc., can result in complicated testing, as you need to test on different versions of those factors.

• Testing is challenging to integrate the existing system with the modern system requirements. It will also increase your testing time to consider new features.

• Sometimes efforts from different teams make the testing incompatible.

• During the testing, it might be challenging to maintain the proper interfaces between different systems without impacting the working of each other.

Integration Testing Best Practices

Some best practices for implementing integration testing will save your time, money, and effort. If you ensure using the best practices from the start of the integration testing process, you can reduce the chances of failure and repeat testing for the same level. We have a few best practices for your consideration.

• Immediately starts integration testing after the completion of unit testing to get consistent feedback from the clients.

• Make sure to define all the details thoroughly about the testing scripts and scenarios for future purposes.

• Also, you can automate the complex tests to speed up the testing process and set what approach you want to use while automating.

• Make sure to use reliable and straightforward testing tools.

• Understand which unit is critical and prioritize them to conduct tests based on the software architecture and design.

• Always prepare a solid test strategy with test cases, making it easier for other members to understand.

• Whenever you write the test cases, always consider every feature to ensure a better user experience.

• Always prepare the mock data before you proceed with the test data.

• Always have the documentation with you for updating it with accurate results.

Integration Testing Tools and Frameworks

Depending on your requirements and ease, you can conduct automated or manual integration testing. But if you consider automated integration testing, you can choose tools testing tools from a vast pool. But we have only mentioned some automation testing tools that will reduce your efforts with productive results.

• Selenium – Timeless Classics

Selenium offers several possibilities for test automation, especially for web-based applications. It has gained wide popularity due to its flexibility and amazing features. Below are some other features that have made their place in the market.

• Multiple languages support C#, Java, JavaScript, PHP, Python, Ruby, and Perl.

• It comes with support for Windows, Mac, Linux operating systems.

• It can efficiently work on different browsers, such as Chrome, Firefox, Safari, and Headless.

• It makes scripting and testing seamless due to its W3C standardization.

• You can run many tests simultaneously without impacting the results of each other.

• You can integrate it with other software solutions.

Apart from this, Selenium comes with one disadvantage - an automation QA engineer should be technically strong.

• Pytest – Python’s Basic Framework

One of the leading testing environments for Python, suitable for writing and running test code. It is well-suited for writing small tests that can scale up accordingly and helps in testing complex applications and libraries. Below are some features:

• You can use this tool to conduct several parallel tests, reducing the overall testing time.

• It defines a test file, and tests feature automatically.

• You can leverage its built-in support for test discovery and command-line.

• Pytest is available as a free, open-source tool providing an active and robust community support.

• Its simple syntax makes ot more popular among beginners.

• RFT – Multifunctional Tool for Test Automation

RTF stands for IBM Rational Functional Tester, a tool for creating scripts like human testers. IBM offers other software to integrate with RFT for a better testing experience. It offers other features that are mentioned below.

• It comes with a storyboard simplifying the test visualization and editing using screenshots.

• You can use recording tools for easy scripting.

• It uses data-driven testing to get the same series of actions.

• You can integrate it with other software for more manageable SDLC management.

• JUnit – a Framework for Running Tests

JUnit is an open-source framework suitable for test-driven development. It is almost similar to Pytest for Python. JUnit is commonly used for conducting automated integration testing, but only for Java programming language. If you are a core Java developer, you should go for this tool for better implementation. It also provides the below features.

• The framework is suitable for writing tests and running tests.

• You can seamlessly integrate this tool with other tools via plugin infrastructure.

• It helps run automatic test results and provides immediate feedback without any manual effort.

• Mockito – a Framework for Mocking

Well-suited framework for Java automation engineers for writing tests. Mockito is considered to be the best framework for Java. Below are some features.

• It comes with a simple API to integrate it with diverse tools.

• It has detailed and thorough documentation with concise reports.

Conclusion

Testing is one of the crucial stages of the SDLC that ensures overall performance and delivers high-end software to clients. Several testing processes are available, but testing the combined working of unit modules requires integration testing that checks for the flow of data between them. It comes with different testing approaches suitable for different scenarios and project sizes. You can run integration tests manually or by automated tools. You can choose any tool depending on the requirement and features offered by those tools. Integration testing has made it easier for developers to determine bugs and fix them at the early stages of development. It reduces time and effort by eliminating the need to fix bugs just before the release.