Component Testing – First Testing in the Project

The first phase is testing the smallest testing unit developed in the Project. A unit can be defined as an isolated piece of code which can be tested independently.Let us take an example, suppose we have to develop an application for an e-commerce site with following requirement.

• Login into System.
• Home Page is displayed.
• Selecting any product and adding to my cart.
• Paying for the Product.

So In this example, we can divide the project development into following components or units.

• Login Module.
• Home Page Module.
• Transaction Page.
• View Cart Module.
• Payment Module.

Before discussing on different testing type. Let us discuss how the development flow takes place. 

• Development team will develop different modules or units of code.
• The modules should be integrated successfully with rest of the modules
• The System developed should be integrated with third party components or existing components.
• The system should work as per requirement document.

As one of the principle of software testing, defects should be captured as early as possible in the software development life cycle. Since the first step in testing is testing the individual module developed. If the individual module has defect, fixing the same can be painful if captured in later stages of SDLC.Unit testing searches for defects in the testable unit or module as discussed. We need to focus on testing the functional features as well as non-functional characteristics.

Let us take the example of unit testing the login module. A login Page needs to be tested as shown below.

The functional test case for the unit will include:

• Error Message on providing invalid username or Password.
• Error Message for minimum and maximum allowed characters.
• On providing successful username/Password, Home Page is displayed. 
• Since Home Page is not yet created, we will use stubs and drivers to dummy for home Page.

The above are examples of functional test cases for components.

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Component testing also includes non-functional characteristics including memory leaks, and structural testing for code coverage. Component testing is done mainly by Developers and is mostly white box testing specially for verification of non-functional validation. Defects are fixed as they are found as is mostly development defect uncovered during dev testing itself.

There are various tools and framework available for unit testing. Junit, testNG are example of framework available for unit testing. Another framework is Test Driven Framework, in which test scripts are prepared before coding. The tests are expected to fail before coding phase. Once Coding is done, all the unit tests are expected to pass. In case, test failing post development, code needs to be fixed until all the tests created for component passed.

Summarizing, all we discussed so far.

Component testing is testing the unit or component or module as an independent unit.
Component Testing is the first testing performed in the project.Component testing is performed mainly by developers.Component testing is more of white box testing on the code.Different Unit testing frameworks are available in the project.

Some Excellent reference article for detailed understanding of Component testing are as follows:

http://www.testingstandards.co.uk/Component%20Testing.pdf

http://people.cs.clemson.edu/~johnmc/joop/col3/column3.html