Unit Testing vs Integration Testing : What’s the Difference?

Unit Testing vs Integration Testing! Do you know what’s the difference between unit testing and integration testing?
Both of them are essential in the development phase as unit testing will evaluate the code you have written for particular feature means while integration testing will ensure that it’s working fine with the rest of the system.
But the difference doesn’t end there.
Let’s make an inch to inch comparison between both the process. Unit Test vs Integration Test!

1) What is UnitTesting:

  • Tests that are conducted by developers for a particular unit of code such as module or component that has been developed by them
  • One of the most effective and simple way to determine if the individual units of source code that are being tested are perfect and ready to use
  • Helps in cutting down the cost of bug fixes as the bugs are identified during the early stages of the software development life cycle (SDLC)

2) What is Integration Testing:

  • A type of testing that tests a product in terms of the integration between its modules
  • Its one of the most effective software testing techniques in which the individual units of a program are combined and tested as a group
  • Executed with the help of test stubs and test drivers that assist in its easy execution

Unit Testing vs Integration Testing – The Differences.

Both these forms of testing have their own significance but it is important to understand the difference between the two:

1. Aim

Unit testing tests each part of the program individually so as to ensure that each of them perform correctly. Whereas, integration testing combines the modules and test them as a group for their optimum functionality.

2. Time of testing

Unit testing is independent and can be performed at any point of SDLC. On the other hand, integration testing is conducted after unit testing is completed and system testing begins.

3. Sub-Divisions

Unit testing cannot be sub-divided whereas integration testing can be divided into top-down integration, bottom-up integration and so on.

4. Integration Errors

Unit testing cannot identify integration errors, or other system-wide errors that exist. Whereas, integration testing can identify all sorts of errors as its purpose is to test and identify errors in modules.

5. Specification

Unit testing begins with the specification of the modules whereas integration testing begins with interface specification.

6. Type of Testing

Unit testing is a form of white-box testing, which refers to testing of internal structure of a program or application. Whereas, integration testing is both white-box and black box testing.

7. External Dependencies

Unit testing does not examine whether a program code works properly with external dependencies whereas integration testing tests the code on the same parameters.

8. Maintenance

Conducted by the software developer oneself, testing a program using unit testing is cheaper as compared to integration testing which is executed by a team of testers.

Unit and Integration Testing are Equally Important

Both these forms of testing have their own importance as the absence of one might impact the overall performance and development of the product.

While unit testing ensures that optimum quality during the development phase of the product, integration testing ensures that there are no errors pending after the development of different modules.
Moreover, identifying the errors during integration testing raises the need for conducting unit testing again so as to identify the specific error in the program.
Therefore, to ensure the premium product delivery, it is better and advisable to keep implementing both these forms of testing as and when required.

What is Integration Testing? Example included

Integration testing is a part of software testing in which individual units are combined together and then tested as a group. It is usually done after unit testing. Integration testing is usually done to rectify the faults that occurred in interfaces and integrated units. Test drivers and test stubs can be used to assist in integration testing.

app testing
What is Integration Testing?
Integration testing is a software testing type to test the logically integrated software modules as a complete group. When software is developed it consists of various independent software modules that might be developed by different developers.
These modules might work well without any defect as an independent unit. But when they are integrated there are changes that bugs can arise while they interact with each other.
In short, their integration with one another may lead to new bugs that were otherwise not present in independent units. To detect such bugs integration testing is conducted.
The process focuses on the communication of data among different modules and is also known as ‘String Testing’, ‘I & T’ (Integration and Testing), or ‘Thread Testing’.
Examples of Integration Test Case
Integration test cases focus on interfaces & flow of data between the test modules. The focus here is integration links testing than testing module functionalities.
Let us take a website with ‘Login Page’, ‘Mailbox’ and ‘Delete emails’. Considering its testing the independent units here are integrated logically.
Let’s not focus on individual module testing rather will focus on the integration of each module with one and another.

Test Case ID Test Case Objective Test Case Description Expected Result
1 Validate Login and Mailbox module interface link Enter the required login credentials and click the Login button Control transferred to Mail Box
2 Validate Mailbox and Delete Mails Module interface link Select an email from the mailbox and click on delete Chosen email sent to Deleted/Trash folder

How to do Integration testing?
We have already read about different integration testing strategies, here is how to execute integration:

  1. Make a Tests Plan for your integration testing
  2. Prepare Test Scenarios, Cases, and Scripts.
  3. Execute the test Cases
  4. Prepare a report and tell the defects to the developers.
  5. Track and retest the defects.
  6. Repeat steps 3 and 4 till Integration testing is successful.

Brief Description of Integration Test Plans:
The integration test plan should include:

  • Scopes and Out of Scopes Items.
  • Roles and Responsibilities of the team.
  • Pre-requisites if any.
  • Testing environment.
  • Risk and Mitigation Plans.

Entry and Exit Criteria of Integration Testing
Entry and exit criteria are very important
Here are they
Entry Criteria:

  • Unit Tested Modules
  • High prioritized bugs fixed and closed
  • complete coding and integration of all modules successfully.
  • Documentation of integration tests Plan, test case, scenarios.
  • Test Environment

Exit Criteria:

  • Successful execution of integration Testing
  • Document of executed Test Cases
  • High prioritized bugs fixed and closed
  • Technical documents
  • Release note

Method of Integration Testing:

Black box testing, white box testing and gray box testing methods can be used for integration testing.

  • Black box testing is also known as behavioral testing. In this design, the internal structure and implementation of the item being tested are not known to the tester. Such tests can be functional or non-functional. Functional testing is the most used one.
  • White box testing is also known as transparent box testing, code-based testing, structural testing, open box testing, clear box testing or glass box testing. In this method, design, internal structure and implementation of the item being tested are known to the tester.
  • Gray box testing is a type of software testing which is a combination of black-box testing and white box testing.

Read Also: Popular Software Testing Misconceptions

Approaches in Integration Testing Services:

  1. Big Bang Approach

In this approach, all the units are combined together and tested at one go. It is usually done when the testing team receives the software as a bundle. Big Bang integration testing tests only the faults in interaction between the units.

It is usually done when the testing team receives the software as a bundle. Big Bang integration testing tests only the faults in interaction between the units.


  • More convenient for small systems


  • It is difficult for fault localization
  • Some interface link can be easily neglected
  • The testing team will get only less time for execution
  • As all modules are tested together, there will be no separate priority given for highly risky critical modules and peripheral modules

2. Incremental Approaches

Logically related two or more modules are joined together and tested.

An incremental approach can be done in two methods:

a. top-down

b. bottom-up

a. Top-Down Approach

In this approach, top-level units are tested first and then lower-level units are tested step by step. In order to stimulate lower-level units test stubs can be added. Test stubs may not be available during the initial phases.


  • Easier fault localization
  • The prototype can be obtained early
  • Design flaws of critical modules can be found and fixed


  • Need for several stubs
  • Lower level modules are tested badly

b. Bottom-up approach

Here bottom levels are tested first and then top levels are tested step by step. Here testers stimulate higher-level units which may not be available during the initial phases.


  • Easier fault localization
  • No time wasted for unnecessary testing of all modules


  • Higher probability for defect as they test critical modules at the very last moment
  • No possibility for an early prototype


3. Sandwich or Hybrid Approach

This approach is an integration of bottom-up and top-down approaches. Hence the advantages of top-down and bottom-up approaches can be applied here also.

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Procedures to be followed for integration testing:

a. Develop the integration test plan

b. Cases, scripts and test scenarios are to be designed

c. Test cases are executed and reporting the defects

d. Defects are tracked and re-tested

e. Repeat step 3 and step 4 after the successful completion of integration testing services

Best practices for integration testing services:

  1. Determine an acceptable integration test strategy and develop test cases and accordingly test data

  1. Analyze the application’s architecture design and identify the critical module.

  1. Interface design can be obtained from the architectural team and you can create test cases to verify all of the interfaces. Interface to external hardware, software application and interface to application must be tested thoroughly.

  1. After completing the test case, the next task is to test data

  1. While executing test cases, it is advisable not to select test data

Integration testing is one of the easiest types of software testing and is one of the crucial steps in the software development life cycle.

How to Master the Art of Cloud Testing

Talks about the use of cloud infrastructure for software testing have been in the limelight for some time now. It is particularly useful in high-stake situations where a company is bound by time and cost constraints.  Along with the advantage of unlimited storage space, its quick availability and flexibility has fueled global acceptance.

app testing

The software industry has changed forever with the introduction of virtualization, which paved way for cloud computing. Hence it is necessary for one to follow the below mentioned steps to ensure effective progress in cloud testing.

  • Understand Cloud Technology: As it is with any business venture, one must first make sense of what is necessary to improve his/her outcomes. Cloud testing can be a completely alien environment even for experienced testers. Thus find time to understand how and where cloud testing can help you in the long run. Understand the benefits of moving a particular testing project into cloud. Remember, cloud testing isn’t the final word when it comes to finding a solution for your testing problems. It is important to conduct unit, functional and integration testing throughout the development cycle.
  • Have Your Own Testing Strategy: Having a well-defined strategy can be the difference between the success and downfall of your testing methods. Have a clear idea about what type of tests should be performed in cloud. You must also be aware about the risks associated with cloud testing.

Weigh the pros and cons of moving to a cloud-based testing.

  • Have a Planned Infrastructure: Moving to cloud testing environment will need careful planning to choose the right kind of testing tools, applications, hardware, software and even bandwidth. Planning should also be done on how long these tools will be in use. That can help with cost reduction and control.
  • Choose the Right Service Provider: Security, quality and reliability should be the most important qualities associated with your service provider. They must be able to provide a quick set-up or tear–down of test environment along with other services like physical infrastructure, testing tools and licenses through provisioning.

Recommended Read:5.41% CAGR for Software Testing Services by 2019

  • Executing the Test: Here the application is tested according to a pre-defined test strategy. You should plan and look for optimal utilization of the test infrastructure in order to realize cost benefits.
  • Monitor and analyze test results: It is necessary to monitor test results in real-time to understand and solve issues concerning capacity or performance. You must even analyze cloud usage against chargeback costs to understand the financial performance of your cloud services.

To master the art of cloud testing for the enhancement of software testing, the following challenges must be overcome:

  • Security: The first and foremost challenge when it comes to cloud technology is security. It must deliver ample user privacy protection and should also meet the security standards on cloud. Hence, if you are to expand software testing into the realm of cloud technology, security testing should be your primary concern.
  • Cloud Compatibility: A great concern for companies when it comes to cloud technology is the performance of their applications, especially in private cloud. Sharing across many users can lead to delays and also cases of maintenance or outage may cause insufficiency of bandwidth.
  • Unsupportive: Sometime with cloud technology, it becomes difficult to emulate the customer environment. This is caused by the unsupportive nature of cloud towards certain configurations for servers, storage or networking that is vital for testing. Therefore make sure whether your application is built to provide the required results on cloud technology.
  • Challenge in Integration Testing: Integration testing is where the tester performs tests on the network, database, servers etc. But with cloud computing, the tester has no control over the underlying environment. This becomes even more challenging when there is interaction between components, with the tester having to anticipate the occurrence of crashes, network breakdown or servers.

Do you think there is more to mastering cloud computing? If yes, please share your thoughts with us in the comment section.