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Difference Between Unit, Functional, Acceptance, and Integration Tests

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Here, we will discuss the differences between unit testing, functional testing, acceptance testing, and integration testing.

Unit Testing

It is a testing technique wherein the simple or smallest units of a software program are examined personally for bugs and errors. These smallest units may be examined independently and personally as they do now no longer want to communicate with every other software program module and are absolutely useful. Unit testing can also additionally require stubs and drivers. These stubs and drivers offer the statistics wished for unit testing and additionally replicate the feature calls.

Techniques of unit testing:

  • Statement Coverage: It guarantees that the testing covers all of the statements in a code. It need to cowl all of the strains of code (LOC) that make up the module this is under testing.
  • Decision Coverage: Software and any software relies upon decision making system and makes use of conditional statements such as though and else. This form of testing makes certain that every condition is included during testing. If the condition is examined, then else condition need to need to be examined.
  • Branch Coverage: Generally packages contain branches and employ break statements or goto statements which reason a bounce from one branch of this system to different. Thus it needs to be ensured that every branch of this system is examined. Most of instances it isn’t viable to check the entire branches. In such instances, it’s far typically suggested to gain minimal 80% branch coverage. McCabe’s cyclomatic complexity metric is used to degree the branch coverage on this form of testing.
  • Condition Coverage: Condition testing includes testing every conditional statement in software together with the while, for, and do-while statements.

Functional Testing

This form of testing includes testing the software program for the useful necessities which are referred to inside the software requirements specification document (SRS). It is accomplished to ensure that at a minimum the simple capabilities of a software program are running well. It is a form of black box testing and exams best the functionalities. It isn’t involved with the supply code. Some styles of useful testing are as follows:

  • Smoke Testing: This form of testing focuses on testing the simple capabilities of the software program and is typically concerned in testing the construct of the software program.
  • Regression Testing: If bugs are discovered in a software program then they want to be fixed. In solving those bugs, new bugs can also additionally arise. This testing is accomplished to test if the old bugs had been resolved and if any new bugs have now no longer arisen inside the software program.
    Integration Testing: All the units are blended collectively to test if they may be speaking well with every different or we will say that they combine with every different with no error. This form of testing is thought as integration testing.
  • User attractiveness testing: After testing the software program for all of the bugs, it’s far examined inside the customer environment. If the customer is glad about the product then the software program is deployed in all of the customer’s machines. This testing is referred to as consumer attractiveness testing.

Acceptance Testing

It is the ultimate level in software program testing earlier than making the software program to be had to be used to the customer. It guarantees that the software program is in keeping with the necessities of the customer and satisfies the customer’s expectations and the necessities referred to within the SRS document. Some styles of attractiveness testing are as follows:

  • User attractiveness testing: After testing the software program for all of the bugs, it’s far examined inside the customer environment. If the customer is glad about the product then the software program is deployed in all of the customer machines. This testing is referred to as consumer attractiveness testing.
  • Business attractiveness testing: This form of testing includes testing whether or not the product or software program meets the enterprise’s purposes, necessities, and goals.
  • Contract attractiveness testing: It is executed to test if the software program fulfills the necessities referred to inside the agreement which is termed a Service Level Agreement (SLA). There is an exact time restriction wherein the agreement necessities need to be fulfilled as soon as the product is going live.

Integration Testing 

A software program typically incorporates numerous modules and applications that undergo unit testing personally. Once the modules are examined personally, they may be included collectively to test how they interact with every different and test any errors that are termed as Integration Testing. It is likewise termed as ‘I & T’ (Integration and Testing), ‘String Testing’, and sometimes ‘Thread Testing’.

Approaches to integration testing:

The following are the technique for integration testing:

  • Big bang technique: In this form of testing, all of the additives and modules of a software program are included as soon as. This form of testing is best useful for small systems. In the case of huge software, it could result in problems. Errors are hard to isolate and pick out in the case of the massive bang technique.
  • Bottom-up technique: In the backside-up technique, the modules at the bottom stage are examined first. Once their testing is complete, they may be included with the modules on the higher layer. The testing keeps till all of the modules are examined and included with the pinnacle stage modules.
  • Top-down technique: This technique is absolutely contrary to the backside-up technique. The maximum stage modules are examined first after which included the bottom stage modules step through step.

Difference between Unit, Functional, Acceptance, and Integration Testing


Unit Testing 

Functional Testing 

Acceptance Testing 

Integration Testing 

DefinitionIt refers to the testing of a software module individually.It refers to the testing of a software module to check if the functional requirements are met or not and whether the module is functioning properly or not.It refers to testing the software on the client side and checking if it functions properly or not in the client environment and the client accepts the software.It refers to integrating the different software modules together and check how they integrate with each other.
DependencyIt needs stubs and drivers to perform the testing of the modules.It does not make use of stubs and drivers.No stubs and drivers are needed.Stubs and drivers are not required.
TypesVarious types of unit testing are statement coverage, branch coverage, decision coverage and conditional coverage.Various types of functional testing are smoke, regression, acceptance, and integration testing.Various types of acceptance testing are user acceptance testing, business acceptance testing, and contract acceptance testing.Various approaches to integration testing are the big bang approach, bottom-up approach, and top-down approach.
StageIt is the first step in any testing process.Functional testing is performed after the unit testing is done.User acceptance testing is the last step in the testing process and is done after the deployment of the software on the client side.Integration testing is done after the unit testing and functional testing are completed.
CostCost of testing is lowThe cost of testing is higher than unit testingCost is lowestCost is highest
Testing techniqueIt uses white box testingIt uses black box testingBlack box testing is followedBlack box testing is followed
ComplexityComplexity is lowComplexity is moderateComplexity is lowComplexity is highest
ExampleFor example, each part of a mobile undergoes unit testing to check if it is working properly.Various functions of each part are checked to see if the desired results are produces=dAfter the mobile phone is ready, it is tested by some internal members of the companyAll the parts of the mobile are integrated together to check if there is coordination between them.

Last Updated : 06 Oct, 2022
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