Updated March 31, 2023
Introduction to Unit Testing
The following article provides an outline for Unit Testing Types. Unit testing means testing the individual ‘units’/ modules of the software application in order to validate that the unit components are working as expected before proceeding for the advanced levels of testing. ‘Unit’ is basically a small testable part of the application tested during the development phase of a software product. Therefore, it is quite easy and time friendly to detect the defects in the early stages of Unit testing. The main aim of Unit testing is to isolate each module, function, method of the application, analyze, test and refactor it to minimize the chances of the issue in the later stages.
Various Unit Testing Types
Unit testing is basically categorized into 3 types which will test the whole application in the smaller units:
1. Black Box Testing
Black box testing is basically software testing in which the internal functionalities, knowledge of the code, implementation details, etc., is not known to the tester. Testing is performed by focusing only on the input/ output of the software application. This testing is also known as the Behavioural testing. The primary source in this testing is the requirements mentioned by the customer and the expected output mentioned for the given input.
In Black box testing, a black box can be any software application, be it a website, databases like oracle or any custom made software. In this testing, a function/ unit of the software is tested by passing the input, and it is checked whether it is producing an expected result or not. If the actual output meets the expected result, it is considered to be as passed otherwise failed. In case of a unit test failure, it is handed to the developer and actions are taken accordingly.
Let us see the generic steps that are followed while performing the black-box testing of an application:
- As the black box testing is based on the requirements of the particular unit, the requirements and specifications of the unit/module are examined.
- The tester and the test data create test scenarios (both positive and negative) to test the module completely.
- For the test scenarios, test cases are created by the testers showing the expected output based on the various inputs.
- The testers now execute test cases.
- After the execution, the expected and the testers compare the actual output.
- The ‘Failed’ test cases are reported to the Developer again, which are corrected and re-tested again.
Some of the important testing techniques involved in the black box testing of the software application are Decision Tables, Boundary Value Analysis, Equivalence Class, State Models, Domain Tests, etc.
2. White Box Testing
White box testing is basically a software testing in which the internal functionalities, implementation, design and coding of software application is tested, and proper flow and output are checked against the provided input. Unlike black-box testing, which focuses only on the functionality, it analyzes the internal structure of the software application. It is also known as Clear box testing, Open box testing, Code-based testing and Glass based testing. As this testing focuses on strengthening the security of the software by testing the input-output flow, a person having good programming skills is required to develop the test cases for it.
The term ‘white box’, ‘glass box’, ‘clear box’ is used for this testing as it provides the ability to see through the application from the outer shell to its inner workings. It is performed by the developers, which tests each line of the code thoroughly. This testing is quite helpful in revealing the “hidden” bugs in the code, broken or poorly structured code, internal security holes, checking of conditional loops, etc.
Let us see the generic steps that are followed while performing the black-box testing of an application:
- As the white box testing is based on working directly on the code, it is important to first understand the code of the application in order to have the complete insight of inner working of it.
- The second step in white box testing is writing the test cases to check the flow and application structure.
- Test cases and now executed by the testers.
- Based on the Actual and Expected results, test cases are marked as Passed or Failed.
- Failed test cases are again reported by the Developer (developing the respective module), which are corrected and retested again.
Some of the important techniques which are involved in White Box testing of an application are Statement Coverage, Branch Coverage, Decision Coverage, Control Flow Coverage, Data Flow Coverage, Path Coverage, Condition Coverage, etc.
3. Gray Box Testing
Gray box testing is a software testing technique in which an application is tested with the partial knowledge of the internal structure and implementation of the software application. It is a combination of Black box and White box testing of the application. Gray Box testing is performed to identify the issues that may arise because of improper code structure or improper use of the software. It increases the testing coverage of the application as it focuses both on the presentation (black box) as well as the internal code (white box).
Gray Box testing is based on UML diagrams, database diagrams, functional specifications, etc. It improves the overall quality of the software application and involves both the developers and testers. For a tester performing the Gray box testing, not too high coding skills are required for them. It mainly focuses on identifying the context-specific bugs that belong to web systems. To perform the Gray Box testing, it is not mandatory for the tester to write the test cases directly from the code, as test cases can be designed based on the knowledge of architecture, high-level description, code knowledge and the basic working of the software product.
Some of the important techniques that are involved in the Gray Box testing are Matrix Testing, Regression Testing, Pattern Testing, Orthogonal Array Testing.
Conclusion
The above description clearly explains what unit testing is and its various types. For any software application, it is important to perform rigorous unit testing on it to ensure that each single unit module of the application is working as expected. Moreover, it reduces the cost of testing as the bugs are identified in the early stages only.
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