What is Black Box Testing?
Black box testing does not require the tester to have any prior information about the software and its internal working. Black box testing is high-level software testing that focuses on software behavior. It includes testing from the point of view of an external party or end-user. This type of testing is applicable in virtually any situation and can be performed at the unit, system, integration, or acceptable level.
Black box testing is a process of quality assurance where the software functionality is not known. The testing is done without internal knowledge of the product being tested. It can be performed using different approaches.
Syntax Driven Tests
This type of black box testing is applied to a system that can be represented in terms of the programming language syntax. In terms of a compiler, the language should have perfect grammar and be free of any errors. The test cases are generated for every grammar rule and applied to the program at least once.
Equivalence Partition
Often many forms of input work in a similar fashion so instead of accounting for all of them separately, it is easier to group them and test the input for each group. The motivation behind black box testing is to divide the input domain into several equivalence classes so that each member of the class operates similarly. This means if a test case in one of the classes results in an error then other members of that class will also be prone to the same error. The method is divided into two steps.
1. Identifying Equivalent Classes
Dividing the input domain into two sets at minimum i.e. valid and invalid cases. The range is defined for each one.
2. Generating Test Cases
Each valid or invalid case is assigned a unique identification number. The black box testing case is written down and it includes all considerations so no two invalid inputs are mistaken for one another.
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Pros and Cons of Black Box Testing
| It is a suitable and efficient option for large code segments | Coverage is limited because only a selected number of test scenarios can be executed. |
| No need for code access | Inefficiency because the tester has limited to no knowledge of the application |
| Separation of the user perspective from the developer’s point of view with clearly defined roles. | Blind coverage does not let the tester target specific segments of code or error-prone areas in black box testing. |
| A large group of testers with moderate experience can test the application with no knowledge of the programming language, implementation, or operating system. | Black box testing case design is complex. |
| Pros |
| It is a suitable and efficient option for large code segments |
| No need for code access |
| Separation of the user perspective from the developer’s point of view with clearly defined roles. |
| A large group of testers with moderate experience can test the application with no knowledge of the programming language, implementation, or operating system. |
| Cons |
| Coverage is limited because only a selected number of test scenarios can be executed. |
| Inefficiency because the tester has limited to no knowledge of the application |
| Blind coverage does not let the tester target specific segments of code or error-prone areas in black box testing. |
| Black box testing case design is complex. |
What is White Box Testing?
White box testing is a technique that checks the internal functioning of any technical system. The testing method is based on complete coverage of code statements, their branches, paths, and conditions. White box testing is low-level testing and it is also referred to as a transparent box, clear box, glass box, or codebase testing. The testing method adopts the logical path in a unit or program under the assumption that it is known.
White box testing analyzes the internal structures of all user data, internal design, code structure, and how the software works. The difference between black box and white box testing is that instead of just testing the functionality like in black box testing, the approach uses structural testing measures for all elements.
The Process of White Box Testing
1- Input
2- Processing
3- Test Planning
4- Output
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Testing Techniques
1- Statement Coverage
3- Loop Testing
2- Branch Coverage
4- Conditional Coverage
5- Basis Path Testing
The process includes making a corresponding control flow graph and calculating their cyclomatic complexity. The testers then find all independent paths and design a test case that corresponds to each one. The technique relies on a flow graph that consists of nodes and edges. Every node represents a series of statements that reach a decision point. The predicate node represents the decision point that follows a condition and after which the graph splits into another branch. Each region is bounded by a node or edge.
Pros and Cons of White Box Testing
| The tester knows the code and it is easy for them to find data useful for testing. | A skilled tester is needed for white box testing which increases costs. |
| It can optimize code | Impossible to look in every corner to find hidden errors and leads to many paths not being tested |
| Testers can delete extra lines of code and remove hidden defects. | Difficult to maintain white box testing because it requires specialized tools for analysis and debugging. |
| The tester has complete knowledge of the code and can cover maximum test scenarios. |
| Pros |
| The tester knows the code and it is easy for them to find data useful for testing. |
| It can optimize code |
| Testers can delete extra lines of code and remove hidden defects. |
| The tester has complete knowledge of the code and can cover maximum test scenarios. |
| Cons |
| A skilled tester is needed for white box testing which increases costs. |
| Impossible to look in every corner to find hidden errors and leads to many paths not being tested |
| Difficult to maintain white box testing because it requires specialized tools for analysis and debugging. |
Difference Between Black Box and White Box Testing
Black box and white box testing are completely different types of tests and follow a divergent structure. They have separate pre-requisites and are only applicable in very specific situations. Black box and white box testing have their pros and cons. While black box testing is less time-consuming it can be inefficient. With white box testing, users have access to more information and cover all grounds.
| Black Box Testing | White Box Testing |
| The internal structure or code is not known to the tester. | The tester has complete knowledge of the internal structure or code. |
| Testing conducted by a specific testing team. | Testing is done by software developers |
| No implementation knowledge is necessary. | Implementation knowledge is required. |
| Referred to as outer or external testing. | Also known as Inner or internal software testing |
| Functional testing technique | Structural testing technique |
| Testing is initiated based on requirements and document specifications. | Testing for the software begins after a detailed design document. |
| No programming language knowledge is necessary. | Mandatory to have programming language knowledge. |
| The software behavior is tested. | The software logic is tested. |
| Higher level of software testing. | A lower level of software testing. |
| Also known as closed testing. | Referred to as clear box testing. |
| It is not time-consuming at all. | The process is very time-consuming. |
| Not suitable for algorithm testing. | Suitable for algorithm testing. |
| Uses the trial and error method. | Tests data domains and internal boundaries. |
| An example is looking up something on Google using keywords. | An example is providing input to verify loops |
| Types include functional, non-functional, and regression testing. | Types include path testing, loop testing, condition testing. |
| Black Box Testing |
| The internal structure or code is not known to the tester. |
| Testing conducted by a specific testing team. |
| No implementation knowledge is necessary. |
| Referred to as outer or external testing. |
| Functional testing technique |
| Testing is initiated based on requirements and document specifications. |
| No programming language knowledge is necessary. |
| The software behavior is tested. |
| Higher level of software testing. |
| Also known as closed testing. |
| It is not time-consuming at all. |
| Not suitable for algorithm testing. |
| Uses the trial and error method. |
| White Box Testing |
| The tester has complete knowledge of the internal structure or code. |
| Testing is done by software developers |
| Implementation knowledge is required. |
| Also known as Inner or internal software testing |
| Structural testing technique |
| Testing for the software begins after a detailed design document. |
| Mandatory to have programming language knowledge. |
| The software logic is tested. |
| A lower level of software testing. |
| Referred to as clear box testing. |
| The process is very time-consuming. |
| Suitable for algorithm testing. |
| Tests data domains and internal boundaries. |
| An example is providing input to verify loops |
| Types include path testing, loop testing, condition testing. |
