Guest Post

Integration Testing Complete Guide

What is integration testing?  

Integration testing involves combining individual units/modules and testing them as a group. This test is conducted to ensure whether two or more separately developed units can work in unison and perform as expected.

Initially, integration testing happened after unit testing for software applications that were developed in a waterfall environment. But after the advent of agile environments, this test can be performed before unit tests as well. Let’s look at some of the advantages of integration testing to understand why it’s so important for the development of software applications.

Advantages of Integration Testing

  1. Integration testing makes testing multiple modules at the same time easier.
  2. Integration testing can be used during different stages of SLDC.
  3. Both bottom-up and top-down techniques can be used to increase the code length coverage in integration testing.
  4. Testing modules at different levels is essential, as it helps you to adjust to the changes in the requirements during the development of software applications.

There are five different types of integration tests, to get a better grasp of what integration testing is let us go through them one by one.

5 Different Types of Integration Testing:  

Big Bang

Big bang integration testing involves integrating all the components and testing them as a unit. These combined components are treated as a single entity, and if either of these components is deficient the process will not execute.


Incremental testing involves the integration of two or more units that are co-dependent on each other and then testing them to ensure that they function adequately. This process continues till every related or co-dependent unit is integrated incrementally and tested.


Bottom-up, as the name suggests, involves testing the lower-level modules first and then moving upwards. This process begins with the testing and integration of lower-level modules and continues moving up till all the modules have been integrated and tested.


Top-down integration testing is the opposite of the bottom-up testing method, here the top-level modules are tested first, and then the flow moves downwards until all the lower-level modules are tested. This method also involves the usage of stubs in case some modules are not ready.


This method is an amalgamation of both bottom-up and top-down testing methods, it involves testing both lower-level and top-level modules together as an integrated system. Also known as hybrid integration testing this method uses both stubs and drivers.

6 Best Practices For Integration Testing

Do integration testing before unit testing:

Everyone knows that it is more expensive to get rid of bugs as the development cycle progresses. That is why testers choose to ensure that every module works perfectly before moving to something as complex as integration testing.

This idea might have seemed senseless not so long ago, but after the advent of the agile development process, this makes perfect sense. The above-stated problems only apply to the archaic waterfall development model, where the testers moved to the next stage only after finishing a stage of testing. Agile testing makes this idea redundant, empowering you to make changes in your applications as you move further in the SDLC.

Bifurcate your tests

Unit tests (fast) and integration (slow) tests should be separated before the testing process is commenced. This grouping should be done using methods provided by your testing framework.

Unit tests only take a few seconds to run, and they also allow developers to refactor ruthlessly without breaking anything.

The slow tests can take many minutes to run as they ensure that the individual components work together. You can deploy CI servers to run integration tests, thus smoothening the entire testing process.

Don’t use integration testing to test your business logic

Running an integration test is a lengthy process. Including them in every build cycle can delay the Software Development Life Cycle (SDLC) by a substantial amount. Business logic should only be tested using unit tests. People often conflate them and end up paying a hefty cost for it.

Unit tests are best for testing the business logic as they are very fast and can be run frequently to detect bugs and fix them immediately.

If there is something wrong during integration testing, it is likely that there is something wrong with the testing environment. Unit tests are potent enough to dispel any bugs that might arise during the testing of your business logic.

Test vital modules at the beginning 

Modules that are most important for the functioning of the application should be tested first. To identify these vital modules, you have to thoroughly study the architectural design of the software. Once you ensure the proper functioning of these modules, proceed to test all the connected modules.

Testing these vital modules will allow you to understand and quantify the functions of all the connected modules.

Log extensively

Integration testing is a complex process that involves the testing of several modules and hardware components together. This complexity makes it hard for a tester to identify any problem that arises during the testing process, thus making it hard for them to fix the issue.

A log can help the tester to get around this issue. Logging extensively helps the tester to maintain the record of the entire integration testing process. Thus, helping testers to narrow down what has or might go wrong during the test.

Identify and use the best tools

The market is full of automated integration testing tools that help you execute test cases and identify defects. Identifying the best tool that helps in solving integration issues in your software is one of the most crucial steps. These tools automate the entire integration testing process, making it convenient for a tester to create and run tests.

Now that we know that integration testing tools are so vital to streamline the integration testing process. Let us look at some of the best integration testing tools and their USPs.

5 Best Tools for Integration Testing:


VectorCAST is one of the most popular tools for performing both unit and Integration Testing. This tool tests each unit individually to make sure that they work as anticipated. After performing the unit test, this tool combines all the units and verifies they perform properly after being integrated.


  • Best for developers who use C or C++ to create their software
  • Streamlines the testing procedure by automating unit and integration tests
  • It validates the safety and business-critical embedded systems


Citrus is an open-source tool that enables automated integration testing by acting as both client and server by simulating the request and response message for message-based applications. Citrus can be used to conduct automation integration testing of Microservices applications, which makes it one of the top tools to conduct integration testing.


  • Creates set sequence of messages and error messages
  • Supports integration testing for message transport connectivity
  • Validate XML response and the existence of data


Liverpool Data Research Associates (LDRA) has been one of the foremost names in the software testing tools market for more than four decades. Their integration testing tool allows you to validate the compliance standards for different organizations. LDRA tool suite integration tests allow testers to provide static and dynamic analysis over multiple platforms.


  • LDRA allows you to easily generate and execute both: unit and integration tests
  • The tool allows you to create a common environment for both unit and integration testing
  • It’s one of the most cost-effective tools in the market


FitNesse is an open-source tool backed by a sizeable community. It’s one of the best tools for business stakeholders as it is a fully integrated self-governing tool that enables you to collaborate effectively. FitNesse is not a UI automation testing tool, but integration with frameworks such as Selenium allows you to conduct UI automation testing.


  • FitNesse only requires you to download a java jar file, and it is operational
  • It provides support to a variety of languages like Java, C#, Python

IBM Rational Functional Tester (RFT)

RFT(earlier known as Green Hat) is an integration testing tool that efficiently maintains test scripts and averts integration problems by helping you manage the entire software development lifecycle by providing you seamless integration with various IBM software.


  • Reduces the time cycle of software by conducting integration testing at the initial stages
  • It offers an agile development process which makes things easier for a tester
  • Enables you to test even if some components are missing by creating code-free, reusable stubs


Integration testing is one of the most important functional tests as it helps you validate those different modules of your application work perfectly in sync. Integration testing should be performed frequently and at the early stages of development. This process might be a little expensive if done properly at the right time of the SDLC, but fixing these bugs, later on, can cost companies a fortune.

The introduction of agile testing methodologies has made the entire process more convenient, as it allows testers to conduct integration testing before or after a unit test.

Enterprises that have adopted agile methodologies and DevOps should adopt integration testing to ensure that the software developed by them works effectively when grouped.