Integration Testing

Integration Testing
Organisations around the world are majorly focused on implementing end to end testing such as, Unit testing and Functional Testing. These tests, though are necessary for accurate development of the software system, should not be the only focus of organisations. It is extremely important for them to spend quality time on testing real use cases, which are usually left for last minute testing. Moreover, there are only few organisations that execute integration testing, which is an extremely beneficial software testing technique, that guarantees fast as well as accurate software development.

Therefore, to signify the importance of this critical software testing technique, elaborated here is a discussion on integration testing.

Software Integration Testing

In a software product there are multiple modules that converse with each other through an interface. Assimilating or integrating these individual software modules and testing them as one is known as Software Integration Testing. Sometimes the integration may form the complete software and yet at other times, it might form a major part of it. The objective of integration testing, which is an extension of unit testing, is to take smaller units of unit testing and test their behavior as a whole.

To know the key differences between unit testing vs integration testing check our new article here.

In this approach integrated modules are tested, where testing always starts at the finest level of the programming hierarchy and continues towards the lower levels. This type of testing is an extension to unit testing.

Features Of Integration Testing:

The prime features of Integration Testing are:

  • Done After Unit Testing is Complete: The most important requisite of Integration Testing is that each module should have been successfully unit tested before the integration can take place. The idea is to ensure that every unit is correctly performing its designated task. Once the performance of each unit is validated it is combined with the next one. At each level of integration, the software is continually tested to make it as foolproof as possible.
  • Integration As Per Test Plan: The integration of every module takes place as described in the test plan. This is done to reduce chaos and have a definitive path that needs to be followed in order to carry out testing effectively.
  • Checks Functionality: The aim behind Software Integration Testing is to guarantee a product that efficiently delivers on all that it promises. As such, at every level of assimilation, the software is rigorously tested to detect and eradicate all functional flaws.

Reasons for Integration Testing:

A software is developed by many individuals with each one handling a particular module. Since the way that each developer uses logic tends to differ from one another, integration testing gives a platform to combine and test all the modules and perform complete software testing. The interface between each module tends to amend or delete values. Such structural data change can be damaging to the software. Integration Testing gives a chance to detect and rectify such errors. Other reasons for integration testing are:

  • Makes sure that the software modules work together appropriately and as per the expectation of the testing team, when integrated with one another.
  • Finds errors in the interface of the software, which further ensures the quality and performance of the product.
  • Ensures that the various modules of the software work in unity.
  • Verifies the functionality, performance, and reliability between the integrated modules.
  • Tackles issues related to inadequate exception handling.

What are the Different Types of Integration Testing?

Integration testing can be classified into four types, each of which is focused on testing the software differently. These types of integration testing are:

  1. Big Bang Integration Testing: In this type of integration testing, all or majority of units are combined together and tested at one go. This approach of integration testing is implemented when the team receives an entire software in a bundle.
  2. Top-Down Integration Testing: Another very significant integration testing approach, top-down integration allows the team to test the top levels of units first, after which lower level units are tested by them step-by-step. It requires stubs to stimulate the lower level units.
  3. Bottom-Up Integration Testing: This approach of integration testing tests the bottom level units first and the upper/top level units. Bottom-up testing requires drivers to stimulate higher level units in the software.
  4. Sandwich Integration Testing: Also known as hybrid integration, sandwich integration testing is a combination of both top-down and bottom-up integration testing. This approach offers advantages of both of these integration testing techniques and helps testers eminently.

Why is Integration Testing Important?

Integration test cases are different from other test cases, it focuses mainly on the interfaces and flow of data and information between the modules. The priority here is given to the integration links rather than the unit function, which are tested already. With integration testing, most of the unit test cases, negative cases, and simpler cases can be written at the earlier stages, which then gets executed on every build. Other benefits of integration testing are:

  • Faster development, a confident level is high.
  • Easy to integrate different modules.
  • It is easy to test.
  • Code coverage is high and easy to track.
  • Provides major assistance in creating real-time use cases.
  • Top-Down or Bottom-Up integration testing starts at early stages of software development and bugs are caught easily.
  • Tests run faster than end to end testing.
  • It easily finds system level issues like, broken database, integration mistakes and more.

Drawback Of Integration Testing:

Apart from offering numerous benefits to the users and testers, integration testing also offers some drawbacks, which can impact the performance as well as the functionality of the product. Hence, to help you be prepared, here are few drawbacks of integration testing:

  • The main flaw in Integration Testing is that any scenario that is not covered in the test plan will be left untouched and as such, critical sources of errors and malfunctions might be overlooked.
  • To be precise the success of Integration Testing lies in the perfection of the test plan.
  • Since test plan is made by humans one needs to cater for its inefficiencies.

Tips for Integration Testing:

Since the significance of integration testing is immense in software testing life cycle, it becomes important for the team of testers to conduct is accurately, which can increase it effectiveness. Hence, here are some tips that can help you test various levels of the software through integration testing.

  • It is vital for the team to have a detailed design document, which defines interactions between each unit of module clearly.
  • Keep the testing suites for integration testing separate from others.
  • Once the software is developed, make sure each unit is unit tested before you initiate integration testing.
  • Automate your testes whenever necessary, such as while using top-down or bottom-up approach of integration testing.
  • Determine a test strategy for integration testing and then prepare test cases and test data accordingly.
  • Finally, do not select test data while execution the test cases.
  • In integration testing, various level/components are combined and tested, which makes it crucial for the team to perform exhaustive logging and reporting during the process.
  • It is best to perform integration testing as frequently as possible.

Implement integration testing on your software product and its various modules effectively with our integration testing checklist.

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Difference Between Integration Testing and System Testing :

Integration Testing System Testing
1. In integration testing, individual units are combined and tested as a group. 1. System testing tests the software application as a whole.
2. Ensures the functionality, reliability, and performance between the integrated module. 2. Ensures the compliance of the developed product with the user requirements.
3. It can be termed as both white box testing and black box testing technique. 3. As this is a black box testing technique, knowledge of internal code is not required.
4. It is also known as Integration & Testing (I&T). 4. Here, test cases stimulate real life scenarios.
5. This type of testing is focused on exposing faults in the interaction between integrated units. 5. It is focused on testing both functional and non-functional attributes of the software.
6. This type of testing is conducted by both testing engineer and software developers. 6. This type of testing is conducted by the testing engineers.
7. Integration testing is performed after the completion of unit testing. 7. System testing is performed after the commencement of integration testing.

Integration Testing Tools: Top 8 2019

The impact of integration testing on various modules of the software product can be increased with the assistance of various automated tools available in the software industry. These simplify the process and make it agile. Hence, here is a list of some of the best integration testing tools:

  1. VectorCAST/C++.
  2. Citrus Integration Testing.
  3. FitNesse.
  4. VectorCAST/Ada.
  5. Protractor.
  6. Rational Integration Tester.
  7. Validata.
  8. Tessy.


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Software Integration Testing is a way to ensure that the complete software, when put together, works flawlessly. In case, the developer overlooked any critical aspect during the unit testing phase, then that is highlighted and in turn, it gives a chance to fix such errors before the final launch. After all, a flawless software is a successful software.

To gain an insight into system integration testing, click here.

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