Before a release, a software application undergoes various operations like extensive testing, iteration, and exception handling to identify bugs and make the software business ready. Integration testing is a primary phase of the software testing process when testing is done at the development stage.
Integration testing is an approach where different components or modules of a software application are tested as a combined entity. You can run integration tests seamlessly regardless of whether one programmer or other programmers code these modules.
This tutorial will give you an overview of integration testing, its importance, types, techniques, and how to perform it.
When separate modules are combined and tested as a whole, this software testing phase is referred to as integration testing. It takes place before the verification and validation process and after the unit testing.
What makes integration testing essential is its ability to check the behavior of different units of a system altogether. When these units are taken individually, they function correctly with almost no errors, but when they are brought together, they uncover incorrect behavior if that exists.
Integration testing is crucial because it's done at an early stage of development and helps prevent serious issues that may arise later by costing high fixing measures. You should run integration tests every time you change the existing code.
Initially, software testing was not dependent on integration testing, and nobody had ever thought about building an advanced testing phase with the capability of finding issues during the development process. But with the growing digital sphere, the demand for integration testing has increased.
Here are some major reasons why integration testing is crucial:
|Unit testing||Integration testing|
|It is a white box testing process.||It is a black box testing process.|
|It is performed by developers.||It is performed by testers.|
|Finding defects is easy as each unit is tested individually.||Finding defects is hard as all modules are tested together.|
|It is always performed first before going through any other testing process.||It is performed after unit testing and before system testing.|
|Developers are aware of the internal design of the software while testing.||Testers are not aware of the internal test design of the software.|
|Integration testing||System testing|
|It ensures all combined units can work together without errors.||To ensure that the total build fills the business requirements and specifications.|
|It is black box testing.||It is a white box and black box testing or grey box testing.|
|It doesn’t fall in the acceptance testing class and performs functional types of tests.||It falls in the acceptance testing class and performs functional and non-functional tests.|
|It is level two testing.||It is level three testing.|
|It identifies majorly interface errors.||It helps to identify system errors.|
Integration testing helps expose any defects that can arise when these components are integrated and need to interact with each other through integration tests.
Integration testing is performed by combining different functional units and testing them to examine the results. There are four types of integration testing, each of which focuses on testing the software differently. Integration testing consists of the following types:
In the incremental testing approach, all logically related modules are integrated, and then testing is done to check the proper functionality of the application as per the requirement. After this, the other related modules are then integrated incrementally, and the process continues until all the integrated, logically related modules are tested successfully.
The incremental approach is carried out by two different methods:
The top-down integration testing approach involves testing top-level units first, and lower-level units will be tested step-by-step. Test Stubs are needed to simulate lower-level units, which can’t be available during the initial phases.
Bottom-up approach involves testing bottom-level units first, followed by the upper-level units testing. In the bottom-up testing approach, test drivers are needed to simulate higher-level units, which may not be available during the initial phases.
|They are mainly used in top-down integration testing.||They are mainly used in bottom-up integration testing.|
|Stubs can be understood as modules of software during the development process.||Drivers are used to invoke the component individually that requires testing.|
|They are crucial to test different features and functionalities of modules.||They are used when the main module of the software is not ready or developed for testing.|
|Stubs play a crucial role when low-level modules are not available.||Drivers get crucial when high-level modules are unavailable or sometimes in the absence of low-level modules.|
|In the case of a partially developed low-level module, you can use Stubs to test the main module.||In the case of a partially developed high-level module, you can use Stubs to test the main module.|
|Stubs are only considered when the upper levels of modules are done.||Drivers can be considered in both cases- When upper-level or lower modules are done.|
The Sandwich testing approach is known as "hybrid testing" because it combines top-down and bottom-up testing approaches. In this strategy, the low modules are tested in conjunction with the higher-level modules and vice versa. This strategy uses both stubs and drivers.
In this non-incremental testing approach, all the developed modules are tested individually and then integrated and tested once again. This is also known as big bang integration testing.
This type of integration testing involves coupling most of the developed modules into a larger system, which is then tested as a whole. This method is very effective for saving time. Test cases and their results must be recorded correctly to streamline the integration process and allow the testing team to achieve its goals.
When the system is ready and the units are successfully tested individually, they can be integrated and tested. The complete process of integration testing includes several steps and has a range of frameworks and continuous integration.
Here's how you can perform integration testing-
Integration testing has both entry and exit criteria that one should know before starting.
Integration test cases mainly focus on the data transfer between the modules as modules/components that are already unit tested, interface between the modules and integrated links.
For example, let's take integration test cases for Linkedin applications:
These are the steps of how LinkedIn works and how Integration test cases are included in testing.
Integration testing usually doesn't require specific tools. These tests are often run manually by QA teams. In most cases, it happens in parallel with the development process, which is the most efficient approach.
First, individual software units are created, and then these units are checked by a development team. After successful checks, QA engineers start combining different units and inspecting them, focusing first on the interfaces and then on the connections between these units.
QA engineers don't require specific tools to inspect these features, even if they are separate.
Regarding automated testing, Selenium is the most widely-used framework for integration testing. If you start with integration testing, don't waste time setting up expensive in-house test infrastructure. Opt for cloud-based testing platforms like LambdaTest. Using LambdaTest's online browser farm, you can run integration tests on 3000+ multiple browsers, devices, and OS combinations.
Its simple onboarding process makes it easy to perform mobile app and web testing. LambdaTest supports automated testing tools like Selenium, Cypress, Playwright, Puppeteer, Appium, Espresso, and XCUITest, among others.
Devs and testers can also leverage LambdaTest’s HyperExecute - an end-to-end test orchestration cloud to run automated tests at a blazing speed of up to 70% more than any other traditional cloud grids.
With the help of automated tools available, integration testing can greatly impact the various modules of the software applications. These simplify the process and make it more agile. Here are some of the best integration testing tools:
Selenium: Selenium is the leading large-scale open-source test automation framework to automate integration test suites for your web applications. Here are some primary features and highlights that make Selenium a top-popular tool:
Pytest: Pytest is widely used for writing and running test code for Python automation testing. It can also scale up and works perfectly while testing complex libraries and applications. Here are some amazing features that make pytest an excellent choice for automated integration testing:
RFT: RFT stands for IBM Rational Functional Tester. It is a popular tool that makes creating scripts that mimic the behavior of human testers easy. To enhance your testing experience, IBM offers different other software solutions that you can integrate with RFT.
Not just maintaining test scripts, RFT provides a couple of different features as well; these are:
VectorCAST: The VectorCAST software testing platform is one of the best in the market to automate testing activities across the software development lifecycle. Advantages of using VectorCAST are-
Embedded developers can use this highly automated unit and integration test tool to validate business-critical embedded systems and safety.
LDRA: LDRA drives the market for software tools that can effortlessly automate code analysis and testing for safety, mission, and business-critical needs. With LDRA, you get-
Like any other testing technique, integration testing also has some challenges that testers and developers encounter. These challenges include-
Before starting your integration testing, you should follow or implement a few best practices.
The main objective of integration testing is to ensure that the entire software system works flawlessly when it is put together. During the unit testing phase, if any critical aspects are overlooked, they are highlighted and, in turn, can be corrected before the final launch.
Integration testing exposes faults in the interaction between integrated units or modules/components. It begins after unit testing has been completed for all modules.
API testing takes place at the message layer without a GUI. As part of integration testing, it determines whether APIs are reliable, fast, and secure and meet the testers' expectations.