Component Testing Explained in Detail

Component Testing

Component testing is a method where testing of each component in an application is done separately.  Suppose, in an application there are 5 components. Testing of each 5 components separately and efficiently is called as component-testing.

  • Component testing is also known as module and program testing.
  • It finds the defects in the module and verifies the functioning of software.
  • Component-testing is done by the tester.
  • Component-testing may be done in isolation from rest of the system depending on the development life cycle model chosen for that particular application.
  • In such case the missing software is replaced by Stubsand Drivers and simulate the interface between the software components in a simple manner.
  • Let’s take an example to understand it in a better way.Suppose there is an application consisting of three modules say, module A, module B and module C. The developer has developed the module B and now wanted to test it. But in order to test the module B completely few of it’s functionalities are dependent on module A and few on module C. But the module A and module C has not been developed yet. In that case to test the module B completely we can replace the module A and module C by stub and drivers as required.
  • Integration testing is followed by the component testing.


  • Stub: 

    A stub is called from the software component to be tested. As shown in the diagram below ‘Stub’ is called by ‘component A’.

  • Driver: 

    A driver calls the component to be tested. As shown in the diagram below ‘component B’ is called by the ‘Driver’.

Below is the diagram of the component-testing:

Component testing

Differences between Unit and Component testing



 Unit Testing


Component Testing
1. Testing individual programs, modules to demonstrate that program executes as per the specification is called Unit Testing. 1. Testing each object or parts of the software separately with or without isolation of other objects is called Component Testing.
2. Its validated against design documents. 2. Its validated against test requirements, use cases.
3. Unit testing is done by Developers. 3. Component testing is done by Testers.
4. Unit testing is done first. 4. Component testing is done after unit testing is complete from the developers end.

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A Soon-to-be Computer Engineer by profession, he has profound devotion to add Data Scientist as a prefix to his name. He’s been to the nooks of the web (at least of the surface web) and planning to add some real figures in his pocket!

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