Black box testing Methods

Black box testing Methods

Graph-based Testing Methods

• Black-box methods based on the nature of the relationships (links) among the program objects (nodes), test cases are designed to traverse the entire graph
• Transaction flow testing (nodes represent steps in some transaction and links represent logical connections between steps that need to be validated)
• Finite state modeling (nodes represent user observable states of the software and links represent transitions between states)
• Data flow modeling (nodes are data objects and links are transformations from one data object to another)
• Timing modeling (nodes are program objects and links are sequential connections between these objects, link weights are required execution times)

Equivalence Partitioning

• Black-box technique that divides the input domain into classes of data from which test cases can be derived
• An ideal test case uncovers a class of errors that might require many arbitrary test cases to be executed before a general error is observed
• Equivalence class guidelines:

1. If input condition specifies a range, one valid and two invalid equivalence classes are defined

2. If an input condition requires a specific value, one valid and two invalid equivalence classes are defined

3. If an input condition specifies a member of a set, one valid and one invalid equivalence class is defined

4. If an input condition is Boolean, one valid and one invalid equivalence class is defined

1.1.3 Boundary Value Analysis

• Black-box technique that focuses on the boundaries of the input domain rather than its center

· BVA guidelines:

1. If input condition specifies a range bounded by values a and b, test cases should include a and b, values just above and just below a and b

2. If an input condition specifies and number of values, test cases should be exercise the minimum and maximum numbers, as well as values just above and just below the minimum and maximum values

3. Apply guidelines 1 and 2 to output conditions, test cases should be designed to produce the minimum and maxim output reports

4. If internal program data structures have boundaries (e.g. size limitations), be certain to test the boundaries

Comparison Testing

• Black-box testing for safety critical systems in which independently developed implementations of redundant systems are tested for conformance to specifications
• Often equivalence class partitioning is used to develop a common set of test cases for each implementation

Orthogonal Array Testing

• Black-box technique that enables the design of a reasonably small set of test cases that provide maximum test coverage
• Focus is on categories of faulty logic likely to be present in the software component (without examining the code)
• Priorities for assessing tests using an orthogonal array

1. Detect and isolate all single mode faults

2. Detect all double mode faults

3. Multimode faults

Specialized Testing

• Graphical user interfaces
• Client/server architectures
• Documentation and help facilities
• Real-time systems

1. Task testing (test each time dependent task independently)

2. Behavioral testing (simulate system response to external events)

3. Intertask testing (check communications errors among tasks)

4. System testing (check interaction of integrated system software and hardware)

Advantages of Black Box Testing

• More effective on larger units of code than glass box testing
• Tester needs no knowledge of implementation, including specific programming languages
• Tester and programmer are independent of each other
• Tests are done from a user's point of view
• Will help to expose any ambiguities or inconsistencies in the specifications

· Test cases can be designed as soon as the specifications are complete

Disadvantages of Black Box Testing

• Only a small number of possible inputs can actually be tested, to test every possible input stream would take nearly forever
• Without clear and concise specifications, test cases are hard to design
• There may be unnecessary repetition of test inputs if the tester is not informed of test cases the programmer has already tried

· May leave many program paths untested

• Cannot be directed toward specific segments of code which may be very complex (and therefore more error prone)

· Most testing related research has been directed toward glass box testing