Unit Testing vs Integration Testing: Understanding the Key Differences

By Prometteur solutions 20 Min Read

4 Important Distinctions Explained

In this article, we will be looking at unit testing vs integration testing. We shall answer the following questions; when comparing unit testing vs integration testing, which one is more beneficial? Can integration testing be done without first conducting unit testing? What is the primary objective of the integration tests that are performed? What are the two different kinds of integration tests? Finally, what exactly are the tools used for unit testing? You will find the answers to all of these questions in this blog. 

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What is Unit Testing?

Unit testing is performed while the program is still in the development process to guarantee that each component of the software carries out the functions that were intended for it by the designer.

The results of unit testing allow developers to determine whether or not the component being tested is ready to be used. During unit testing, a specific section of the program is separated from the rest of the application so that it may be evaluated independently. Developers are able to find flaws at an earlier stage of development by using the isolation approach, which helps maintain the cost of repairing defects at a lower level.

What is “integration testing”?

Integration testing is a sort of software testing in which the various units, modules, or components of a software application are examined as a united entity. This type of testing is referred to as testing at the integration level. Integration testing verifies that two distinct modules can function together without causing any disruptions.

Integration testing enables developers to merge multiple modules of independent software into a single product. This process of combining the modules into a single product is called integration. This type of testing determines whether or not the two modules are able to interact with one another correctly.

Developers may imitate the missing component of a software module that is preventing seamless communication by using dummy programs. This is because the module is incomplete. After that, they may include that module portion into the coding.

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What is integration testing components

The process of determining whether or not two software components are compatible with one another is referred to as integration testing.

Why should we bother with integration testing? 

A module may perform well in isolation but encounter integration problems when interacting with another module. For example, the modules may have data type or valid data range difficulties. 

It is essential in big teams when modules are built by separate developers or even teams because there may be a gap in the understanding of the various developers. 

What are the Benefits of Integration Testing?

  • As previously said, it aids in finding integration difficulties across modules. 
  • It helps verify that the Integration modules function correctly before proceeding to system testing the whole program. 
  • Bugs discovered at this level are simpler to address than those discovered at higher phases of testing, such as system and acceptability testing. 
  • It increases test coverage and adds another degree of dependability.

The primary distinctions between unit testing and integration testing are listed below.

Size of the team

When doing unit testing, a group of developers are optional to examine individual parts of code. Testing of individual software components may be performed simply by a single developer.

On the other hand, integration testing calls for a group of programmers to work together. Regarding system integration testing, the team of developers is responsible for preparing test plans, designing test cases, running many tests, identifying important flaws, and fixing them.

Code accessibility

Accessibility of the code is required in order to execute unit testing since developers need to inspect the code that has been created.

Integration testing, as opposed to unit testing, does not need the accessibility of the code; rather, developers need to evaluate the interfaces and the interactions between modules.

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What Are The Benefits Of Unit Testing

Some developers need to pay more attention to the value of unit testing. Here are five unit testing advantages that you should consider before making your decision.

Bugs are discovered quickly and simply

Code that has been tested is more trustworthy than code that has not been tested. If a future modification breaks anything in the code, developers will be able to pinpoint the problem’s source immediately rather than having to search through an unmanageable codebase.

Best practices recommend that developers run all unit tests or a set of tests locally first to ensure that any coding changes do not impact the current code. Consider the human component, however: After making changes, a developer may need to remember to run unit tests and publish possibly broken code to a common branch. Many businesses use a continuous development method to prevent this. Continuous integration tools are used for this, which enable developers to run unit tests automatically. A cool, logical computer will therefore identify any undesired modifications in the code.

The speed with which non-working code is detected is determined by the tools used for continuous integration. For example, tests may be configured to execute a one-time check at a predetermined time interval or to run instantly in real-time to examine changes.

In summary, unit tests enable developers to notice and correct issues as they occur. As a result, teams may move on to the next phase of a project with less resources spent on bug hunting.

Unit testing conserves both time and money.

When unit tests are performed, many flaws are discovered during the software building stage, preventing these bugs from progressing to later stages, even after the product is released. This reduces the expense of correcting issues later in the development lifecycle and helps end customers by removing the need to cope with a defective product. You will also benefit tremendously from enhanced test time estimates, which will save you a significant amount of time and money.

Unit testing is an essential component of extreme programming

Unit tests are required for the Extreme Programming technique to work. Extreme programming is simply a method of “testing anything that might possibly fail.” Writing unit tests using this technique simplifies development and code reworking, facilitates integration, and generates live documentation. This leads us to our next point.

Unit testing generates documentation.

Unit tests serve as live documentation for the product. Developers may use unit tests to acquire a basic view of the logic of the module and the system as a whole to discover what functionality is offered by one module or another. In addition, unit test cases are indications that provide information about the proper or incorrect usage of a software component. As a result, these situations provide ideal documentation for these indications.

Reusable and Trustworthy

Individual modules of a product become segregated from one another and have their own area of responsibility inside unit testing environments. That implies the code is more reliable—it was tested in a controlled environment—and hence reusable. Reusable code benefits everyone since it is clean, efficient, and consistent. Unit testing accelerates all of this.

Unit testing aids in performance evaluation.

It would be great if you could identify potential flaws in your software before it gets into production and users discover them on their own. Unit tests give such an opportunity, avoiding the needless work of looking for answers to non-existent problems. For example, if you deal with a hashed list, you may need to test how it will function as the list expands. The pace of expansion could be clearer. From here, you’ll most likely use unit tests to test situations with varied degrees of likelihood, ranging from extremely plausible to ludicrous. If you are already certain that the number of items in the hashed list will not exceed 10,000 under any circumstances, you are done and may stop at 100,000. You have shown that your software capability is enough, and there is no need to spend more time testing.

Code coverage is increased through unit testing.

It’s quite important to determine during the active code development stage if a certain line will ever be run or whether you can safely eliminate it. If you have appropriate unit tests, you can immediately get coverage numbers and assess if a code line is ever useful. Try adding one more test to your code coverage if it isn’t. Remove any superfluous code if your test suite currently covers all potential situations. However, the requirement for further testing indicates that cyclomatic complexity is growing.

Code complexity is reduced via unit testing.

Cyclomatic complexity is a quantitative metric that may be used to determine how difficult a program and its code are. The greater the number of pathways suggested in a single code block, the greater the complexity. When there is no control flow statement in the source code, the complexity rate is one, progressively growing to two or higher using “if” statements. As you would expect, attaining perfect unit-test coverage gets challenging at this point. The more conditional statements there are in the code, the more complicated the code block.

When writing unit tests becomes difficult, it indicates that the code may also be overcomplicated. However, without unit tests that objectively answer the issue of whether or not your code works, all you have is your own assumption. Unit tests provide actual evidence.


All of the criteria mentioned above are interrelated, implying that unit testing unquestionably helps to the improvement of your program. Unit testing may seem to be time-consuming, but the advantages are obvious in the long run. Before code is deployed, unit testing verifies that it fulfills quality criteria. This offers a dependable engineering environment where quality is of the utmost importance. As a result, unit testing saves time and money across the product development life cycle and helps developers create better code more effectively.

Unit testing vs integration testing: implications for the whole system

Testing individual software components and modules is known as “software unit testing.” The developers test only the code and the functioning of the program. They do not test any of the system’s problems.

The testing of system integration looks for any connections that may exist between two or more components. When developers do this, they check for any faults that may affect the whole system and are caused by the modules that are utilized for integration.

Comparing the benefits of unit testing to integration testing: Bug detection

The developers inspect the  code, identify the problem, and then update the code to correct the problem, thus finding bugs during software unit testing is straightforward.

On the other hand, finding bugs during system integration testing takes a longer amount of time since developers need first to determine the cause of the issue, then locate a solution to the problem, and last test how well the revised strategy works.

Other significant distinctions

The primary distinctions between unit testing and integration testing

Principal distinctions between Integration testing and individual testing units

What are some of the most prevalent tools used for unit testing?

The following is a list of common testing tools for individual units:

Junit is a tool that assists in the execution of unit tests for software applications written in the Java programming language. Testing software data and code is made easier using Junit, which also provides assertions relevant to the currently used testing approach.

PHPUnit: PHP programmers may use PHPUnit for software unit testing, which enables you to verify individual portions of code in relatively tiny increments of code.

JMockit is an open-source tool for unit testing built on top of the Java framework. JMockit provides assistance in simulating objects during testing and makes use of instrumentation APIs to modify code while it is being executed.

Related Post: Seven Well-Known Open Source Programs That You Should Check Out

What are the typical techniques used while doing integration tests?

Integration testing may be handled in a variety of ways, some of which are as follows:

Big bang testing

Integration testing requires the developers of a system to bring together all of the system’s components into a single entity in order to test the system.

Testing from the top down

Using this approach, the developers test the modules in reverse order, beginning with the most recently added. When evaluating the integration of a system from the top down, the top modules are examined first before going on to the bottom components.

Bottom-up testing

This strategy puts the modules through their paces in reverse order. When testing system integration from the bottom up, the lower modules are examined first before going on to the higher components.


By inspecting the program’s source code, unit testing establishes whether or not a specific component or portion of the software functions as anticipated. Integration testing, on the other hand, is what assesses whether or not a software system’s various components can communicate with one another.

The software development cycle includes many essential phases, including unit testing, integration testing, and system testing. As a result, businesses may develop excellent software in a more expedient and timely way with the assistance of developers experienced with unit testing or integration testing.

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What are the two primary categories of unit tests?

Testing a unit may be done manually or automatically, and both are considered to be forms of unit testing. The code is produced by hand in manual unit testing, but in automated unit testing, a code script that solves common problems is generated from previously written code.

Can integration testing be separated from functional testing?

Not at all; functional testing does not include integration testing in any way. Instead, integration testing examines how a system’s various modules interact, while functional testing examines how each component of a software program performs its intended role.

What are the different stages of the integration test?

Integration testing involves a series of stages, including the creation of a test strategy, the design of test cases, test scenarios, use cases, and scripts; the integration of modules; the detection and correction of errors; and the retesting of functions.

What is Unit Testing?

Unit testing is performed while the program is still developing to guarantee that each component of the software carries out the functions intended for it by the designer.

What exactly is “integration testing”?

Integration testing is a sort of software testing in which the various units, modules, or components of a software application are examined as a united entity. This type of testing is referred to as testing at the integration level. Integration testing verifies that two distinct modules can function together without causing any disruptions.

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