What Is Integration Testing? Types, Tools, and Best Practices

Integration testing is defined as a software testing process where a group of software components, modules, or units are tested to evaluate system compliance with respect to functional requirements.

What Is Integration Testing?

Integration testing is a software testing process where software components, modules, or units are tested to evaluate system compliance concerning functional requirements.

Integration testing is the second level of the software testing process after the unit testing process. This testing phase is crucial to ensure seamless interactions among various units/components, their functionalities, and how well they can operate as a single entity. The following are the steps for integration testing:

1. Craft integration testing plan

The first step of integration testing is to craft a complete integration testing plan, including which units need to be tested, the key goals of testing, what functionalities and interactions to check, and how to ensure optimum operability for the system units. This will help execute the integration testing process and give a clear idea of what to expect.

2. Define relevant tests & use cases

A test case refers to a specific set of inputs, testing methods, execution conditions, and expected test outputs or results. Use cases, on the other hand, define the applicability of the testing process. 

Based on specific software units, features, software development requirements, and other factors, one needs to determine the test and use cases for unit testing to execute the integration testing efficiently.

3. Run testing method

Various integration testing methods exist, such as risky-hardest, top-down, big-bang, and others. Integration testing is executed through a black box testing approach where the testers utilize the software interface to interact with it. In integration testing, the focus is not on the codes or how they work but on how they function, which is tested through the interface.

4. Scan & detect errors

This stage is dedicated to running an in-depth scan to find any possible errors in the combined functionalities of the software units, modules, or components. This step helps find out whether the software components are functioning correctly and interacting with each other. Gaps or issues are needed to be fixed after this stage.

5. Retest after fixing errors

Once the issues are fixed after the initial testing, retesting is done to ensure that there are no bugs and the previous ones are fixed completely. This stage is vital to ensure the optimum functionality of a system or software and make it completely error-free.

6. Retest to eliminate all errors

This is the last and final stage of integration testing. As the name suggests, retesting should be performed repeatedly until all the issues or bugs are fixed, and optimum software quality and functionality are achieved.

See More: What Is TDD (Test Driven Development)? Process, Importance, and Limitations

Types Of Integration Testing

The four types of integration testing are:

1. Top-down integration testing

Top-down integration testing is a famous approach focusing first on the main module and then on its other sub-modules and subroutines. Here, the sub-modules and sub-routines function as temporary counterparts and generate outputs similar to the existing software. 

As the main module or routine is emphasized first in this type of testing, and then the testing for sub-modules and sub-routines are executed, it is called top-down integration testing.

2. Bottom-up integration testing

In bottom-up integration testing, the testing process for the sub-modules or sub-routines is done first, and then the main module or routine is tested.

Bottom-up testing is also considered an incremental method where two or more sub-modules or sub-routines are combined and tested first. Then gradually, the main module is tested. This is also the reason why it’s called bottom-up integration testing.

3. Mixed/sandwich integration testing

Sandwich integration testing or mixed integration testing refers to a hybrid integration testing process that combines the top-down and bottom-up integration testing methods. Since it utilizes the positive sides of both these integration testing methods, it is highly sought-after by testers. 

In sandwich integration testing, the sub-modules are tested along with the upper-level modules, while the top-level modules are integrated with the sub-modules for testing purposes. This makes integration testing more efficient, cost-effective, and time-efficient. 

4. Big-bang integration testing

Big-bang integration testing is quite popular among testers, especially hose who don’t want to go through the modules and sub-modules testing approaches and prefer a faster testing process. 

In big-bang integration testing, all the system modules, components, or units are connected as a single unit or software and the testing is executed on it as a whole. While this is a more accessible and simpler approach for software testing, bug detection & isolation and individual interface testing often become challenging with this approach.

See More: What is Root-Cause Analysis? Working, Templates, and Examples

Best Practices Of Integration Testing

One can take different approaches to perform integration testing, and one needs to know the best practices and strategies to leverage them at their best. Let’s have a look at the top best practices for integration testing.

1. Maintain dedicated test suites

Maintaining separate and dedicated test suites is recommended to ensure that unit testing and integration testing are executed separately to avoid complexities and make them even more purposeful. 

Since testers often require prompt feedback through unit tests, the test suites may require additional time and space. In such a scenario, keeping the test suites separate and running the testing processes separately is recommended. Also, the lack of maintenance of unit testing infrastructure may result in an overall delay in the testing and software delivery process. The best practice to avoid such a scenario is dedicating separate suites for integration testing and unit testing. 

2. Keep business logic separate

To avoid complexities related to integration testing and unit testing, it is recommended to refrain from testing business logic along with integration testing. Whenever any build is triggered in a CI environment, testers prefer to execute unit testing as it works faster than other testing methods and fulfills the requirement of testing the efficiency of each software unit. 

This is why unit testing is executed to check for issues or bugs in business logic and fix them immediately. On the other hand, integration testing is more time-consuming and complex than unit testing, so it’s not recommended to run integration testing for every business logic. The best practice will be keeping the business logic separate from integration testing and testing them as units through unit testing.

3. Leverage the scope of extensive logging

No matter what type of software it is, if it’s small, one can test and fix issues through unit testing. It lets you quickly test any software with a particular scope and helps detect and fix problems in case the unit testing process fails. 

Integration testing, on the other hand, involves different software modules and sub-modules. The scope involves different software components, functionalities, and interactions in such a case. As a result, if integration testing fails, detecting and fixing the cause may take more time, and the process becomes quite complex. 

In this scenario, extensive or exhaustive logging comes into play, which helps detect and fix the cause of the failure by considering the software’s different components. While it is recommended to keep the provision and scope of extensive logging, it should only be adopted when required, as this may affect the performance of the testing process.

See More: What Is Penetration Testing? Types, Methods, and Best Practices

Top 9 Tools For Integration Testing

One needs to adopt the right integration testing tools to execute the integration testing process efficiently. Here’s a list of the top nine tools that you can opt for integration testing:

1. Citrus

CitrusOpens a new window is a popular integration testing tool based on Java and is suitable for integration testing for diverse applications and data formats. Be it response data and plain text messaging request or JSON or XML, Citrus facilitates them all through diverse protocols such as SOAP (Simple Object Access Protocol), JMS (Java Message Service), and HTTP (HyperText Transfer Protocol), to name a few. 

Some of its top features that can improve integration testing are:

• Easy-to-use and open source
• Helps in advanced data and header validation
• Can act as both client and consumer by exchanging request/response message
• Test automation that can run as integration testing in CI/CD pipeline

2. SITA (Smart Integration Test Accelerator)

SITA or Smart Integration Test AcceleratorOpens a new window is a widely used integration testing tool that operates with a business-centric approach. It lets one execute and streamline the integration testing process for diverse systems and use cases and simplifies the complexities of testing through approaches such as bottom-up. 

Some of its top features that help execute integration testing are:

• Simplifies the process flow of integration testing and minimizes the time taken
• It helps generate test data easily
• Automate diverse test design activities
• Facilitates the reusability of a broad range of test cases and test data 
• Allows the utilization of its potential by easily integrating it with diverse tools such as HP ALM, IBM Rational, and others

3. LDRA

LDRAOpens a new window is one of the top integration testing tools that help achieve the best possible software quality. Dominating the software testing market for more than 40 years, LDRA helps adhere to different software compliance standards and helps one easily run a complete analysis through integration testing.

Its TBrun and LDRAunit are the most popular among software testers, meant to achieve high software quality and improved interaction among modules through integration testing.

Here’s a list of the top features of LDRA that help in integration testing:

• Offers a compact and dynamic solution for integration testing for various types of software 
• Provides a tailored solution for integration testing as per the specific requirements of a software
• Gives highly cost-effective solutions for integration testing as well as unit testing to ensure the functionalities of each of the software units as well as the whole software

4. Rational Integration Tester

Formerly known as Green Hat and acquired by IBM in 2012, Rational Integration TesterOpens a new window is the most suitable for integration testing in use cases such as SOA (Service Oriented Architecture) messaging tests, integration, and other relevant projects. 

Not only does it help reduce crucial integration issues, bugs, and errors but it also helps adopt an iterative approach for the best possible result.

Let’s have a look at its top features:

• Lets one create an advanced and suitable scripting-free environment
• Enables the creation of reusable stubs that are free from coding and carry on with the testing even in cases of missing software modules
• Offers an Agile development and testing solution to bring out the best in the integration testing process
• Helps in implementing a time-efficient integration testing process

5. Tessy 

TessyOpens a new window is a highly sought-after integration testing tool by software testers. It is the most suitable for the unit testing of embedded software and helps analyze and identify the code coverage for any software. Furthermore, its CTE (Classification Tree Editor) helps define diverse test cases through a systematic approach. 

These are its key features:

• Lets one quickly analyze diverse system interfaces and functions
• Provides compact analysis and testing functions for TIE (Test Interface Editor), Test Data Editor (TDE), and Workspace
• Helps with test execution, test results, and test analysis
• Offers compact support for code coverage

6. Validata MSG

Validata MSGOpens a new window is a widely used integration testing tool focused on automating the integration testing process and increasing its efficiency. It provides a compact framework for automation testing for SWIFT, SOA, ATM, and other generic interfaces. 

This integration testing tool reduces the complexities of integration testing and the time taken to execute integration testing, as well as helps stimulate different types of business use cases and test cases to make integration testing even more effective. 

Some of the key features of this integration testing tool are:

• Offers a cutting-edge test automation solution
• Provides a range of end-to-end business cases and scenarios for efficient integration testing
• It comes with an all-in-one solution to ensure file formatting, data content and improved testing process flow
• Lets one leverage its broad range of pre-built test scenarios to make integration testing even more efficient
• Offers dedicated solutions to schedule, test, and validate SWIFT, ATM, SOA, and others.

7. Protractor

Dedicated to ensuring better integration testing for Angular and AngularJS applications, ProtractorOpens a new window works as a wrapper around Selenium web driver. It provides a complete framework for automated integration testing and helps stimulate user interaction with Angular web applications for several use cases and test cases. 

One of its unique advantages is that it comprises Angular-based features and the key features of Selenium WebDriver. This popular web framework enables one to perform cross-browser tests easily.

Let’s have a look at some of the prime features of Protractor:

• Offers completely managed end-to-end frameworks for the integration testing of Angular and AngularJS applications
• Utilizes browser-based drivers and various native events to stimulate user interactions with software
• Comes with diverse locator strategies that are focused on automating and improving the integration testing of Angular products 
• Offers a compact automated waiting and execution process that bypasses the hassles of manually adding waits and sleeps

8. VectorCAST/C++

VectorCAST/C++Opens a new window helps build a strong foundation for integration testing and improves the whole integration testing process. It helps test each module, component, or routine of software to ensure that they are functioning correctly individually and that there are no bugs or errors. It also lets one run integration testing after combining all these components and modules to check their interactions and functionalities. 

Here’s a list of the top features of the integration testing tool VectorCAST/C++:

• Offers a complete integrated code coverage utility
• Equipped with a completely automated framework to facilitate automated integration testing
• Provides a range of integration testing solutions for diverse embedded systems with differential business cases
• Equipped with an advanced dynamic test solution that fits the integration testing requirements of various software–healthcare & medical software, SaaS products, industrial software, and others
• Comes with an advanced solution to implement and execute diverse repetitive and consistent processes related to integration testing

9. VectorCAST/Ada

VectorCAST/AdaOpens a new window is an integration testing tool that you can easily integrate with other tools such as IBM Rational, Green Hills, and others to make integration testing even more powerful. It lets you perform integration testing for several test cases, use cases, and business cases as required for software. 

Another key advantage of using this integration testing tool is that it automates the process of drivers and stub creation through its simple-to-use code generator.

Here are some of its top features to leverage for integration testing:

• Offers a range of dynamic software testing solutions for integration testing requirements
• It comes with an advanced integration testing solution suitable for embedded developers
• Provides an easy solution for integration testing execution from GUI (Graphical User Interface) and scripts
• Equipped with an in-depth code complexity analysis and risk highlighting feature that offers better outputs from integration testing 
• It lets you utilize the present existing tests to facilitate automated regression testing
• Offers an easy integration solution with a range of systems and software, including IBM® Rational® Rhapsody®, DDC-I™ SCORE®, IBM® Rational® DOORS®, AdaCore GNAT, Green Hills® AdaMULTI™, Atego™ ObjectAda®, and other tools
• Offers complete automation for simulator test execution for diverse test and business cases
• Provides an end-to-end solution for on-target testing processes
• Automates the execution process of stub codes and drivers deployment

See More: What Is Regression Testing? Definition, Techniques, and Tools

Takeaway

Integration testing is crucial in ensuring functionality and interactions among various software modules. Hence, it is used widely in testing different types of software in diverse sectors, from SaaS to eCommerce. However, it is recommended to execute integration testing after unit testing to test the individual unit’s functionalities and the functionalities and interactions among these units to ensure optimum software quality.

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