Difference Between Structural and Functional Testing

Difference Between Structural and Functional Testing: Structural and functional testing is a form of testing performed to evaluate the response of software & computer hardware to various stimuli. In Structural Testing, software application functionality is verified by performing tests that exercise each individual module in isolation. Each module can be tested independently. In Functional Testing, it is verified by performing tests that exercise specified combinations of related modules. It is performed to verify whether the software meets the expected requirements and to detect functional errors.

Structural Testing

Structural testing is a black-box testing method or software testing technique in which software’s structural elements such as modules, components, and objects are tested for proper interface and interaction. Structural Test is performed without seeing the internal implementation details of the code structure.

Examples of structural testing techniques are:

1. Statement Coverage:

Statement coverage is a white box testing technique. It involves executing each line of executable code at least once to ensure that all possible paths are explored through the code. In unit testing, statement coverage is often applied to small segments of code and measured on an individual basis.

2. Data Flow Testing:

Data flow testing is a method for checking the internal logical consistency of a complex system. It is a white box testing technique that involves analyzing the control-flow diagram of the code or its equivalent and then finding test cases that cover every decision point and data store in that structure.

3. Path Coverage:

Path coverage requires that every branch in the control flow graph be executed at least once. In general, branch coverage is easier to attain than statement coverage because not all statements need to be executed, only those branches that lead to executable code; these are called decision or branching statements.

4. Branch Coverage:

Branch Coverage, or Decision Coverage, is a white box testing technique. It involves executing each branch at least once to ensure that all possible paths are explored through the code. In unit testing, branch coverage is often applied to small segments of code and measured on an individual basis.

5. Traceability Matrix Analysis:

Traceability Matrix Analysis is an analysis tool for requirements-based testing and describes how test items are linked to the corresponding requirement attributes.

Functional Testing:

Functional testing is a type of black-box testing that bases its test cases on the specifications of the software component being tested. It determines if the component under test behaves as specified in the functional specification or user requirements document. It is performed by executing representative sequences of inputs, which correspond to the desired functional requirements.

Functional testing has five levels – Unit, Integration, System, Acceptance, and Regression:

Unit Testing: In unit testing, it is verified whether each software module works as expected by performing a set of test cases on the individual modules. It focuses mainly on individual components, methods, classes, or functions. Unit testing is performed after module coding and before integration testing.

Integration Testing: In integration testing, all the modules are tested to verify whether they operate correctly when they are combined with other software modules.

System Testing: In system testing, it is verified whether the entire integrated application meets the requirements of its users and works as expected.

Regression Testing: In regression testing, it is verified whether changes to the software components have not affected the existing functionalities and features. It is performed after every major code change.

Acceptance Testing: In acceptance testing, it is verified whether specified users are satisfied with application functionality & performance.

Difference Between Structural and Functional Testing

Here are some of the differences between the two:

Structural Testing	Functional Testing
Structural testing is done in manual mode.	Functional testing can be performed either manually or automatically.
Structural test cases are designed based on external specifications and internal code structure is not considered	Functional testing would depend on both external specifications and the internal workings of the component.
Structural test cases are based on input/output conditions	Functional test cases are based on actions that a component can perform.
Structural testing is used to find errors in data structure usage and internal coding logic.	Functional testing verifies that the system adheres to acceptable standards of information processing and does not contain any defects.
Structural testing is done after the coding process is completed by maintenance groups.	Functional testing is performed during development and/or maintenance.
Structural test cases do not depend on data values.	Functional test cases may have to use some specific value for a test case to pass or fail (error checking).
Structural test cases are based on hardware level error checking.	Functional testing is achieved by software techniques.
Structural testing involves static data structures and algorithms.	Functional testing involves the analysis of dynamic data structures and object-oriented programming.
structural testing addresses error detection and repair.	Functional Testing may address quality attributes such as reliability, maintainability, security, etc.
Structural testing mainly focuses on logical errors or bugs in the code	functional testing focuses on verifying that the system meets its requirements.
The structural Testing tool is based on data flow analysis methodologies	The functional Testing tool is based on the Event Analysis methodology.
Structural Testing is used to test the functional elements of an application, such as a text display feature and how it works with other features.	Functional Testing is carried out based on the business requirements of the application and looks at the user’s acceptance criteria to how well the system meets the user’s needs.
Structural Testing is performed on low-level modules/software components	Functional Testing is performed on the entire software system as per required specifications.
Structural testing does not recognize any boundary conditions as per requirement criteria	Functional testing accepts all boundary conditions.
Structural Testing looks at input/output conditions rather than actions that a component can perform	Functional Testing is concerned with the way an application behaves in terms of its business domain and satisfies the user’s needs.
Structural Testing is mainly used for testing intercommunication between modules	Functional Testing would look at how well the system satisfies a certain business purpose or set of business purposes.
Functional Testing has objective criteria to pass or fail	Structural Testing may have some subjective interpretation of the result.
Structural Test Cases are usually carried out by a software development group	Functional test cases are designed by business analysts and testers.
Structural Testing provides information about the internal design of the module being tested. Hence it can provide constructive information towards improving the internal design of the module/software application.	Functional Testing provides information about how well the system meets the user’s needs and also helps in discovering defects that may lead to business loss.
Structural Testing is used for testing systems that are interconnected.	functional testing could be used to test stand-alone applications.

Conclusion:

It is clear that Structural Testing and Functional Testing are used for different purposes. Both types of testing are important in their own way to get robust software applications but these two types of testing are quite different from each other.

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