Blackbox

BLACKBOX TESTING TECHNIQUES

1. Black Box Testing

2. Only input & output functionality are visible. Inputs are given and outputs are compared against specification. Features: Correct outputs from inputs properly. Test cases are designed from user requirements. Test planning can begin early in the software process. Looking at the program from an external point of view.

3. Black Box Testing Input Test Data I System output Test Results O Inputs causing anomalous behavior Outputs which reveal the presence of defects

4. Black Box Testing is a “Expert” in Finding Incorrect or missing functions. Interface errors Behavior or performance errors. Initialization and termination errors. Errors in data structures External database errors.

5. Graph Based Testing Methods Each and every application is build up of some objects. All such objects are identified and graph is prepared. From this object graph each object relationship is identified and test cases written accordingly to discover the errors.

6. Sample Graph Notation Object 1 Object 2 Object 3 Directed Link Parallel Link Undirected Link or Bidirectional Nodes are represented as circles. Links between nodes are categorized as: Directed Link (one direction) Bidirectional or Undirected or Symmetric Link: both directions. Parceled links: different relationships established between nodes.

7. Error Guessing Testing Methods This is purely based on previous experience and judgment of tester. Error Guessing is the art of guessing where errors can be hidden. For this technique there are no specific tools, writing the test cases that cover all the application paths.

8. Methods of Black box Testing

9. 1. Equivalence Partitioning Equivalence Partitioning is a software test design technique that involves dividing input values into valid and invalid partitions and selecting representative values from each partition as test data .

10. 2. Boundary Value Analysis (BVA) Boundary Value Analysis is a software test design technique that involves determination of boundaries for input values and selecting values that are at the boundaries and just inside/outside of the boundaries as test data.

11. 3. Cause Effect Graphing Cause Effect Graphing is a software test design technique that involves identifying the cases (input conditions) and effects (output conditions), producing a Cause-Effect Graph, and generating test cases accordingly.

12. 4. Orthogonal Array Testing Used to finding errors associated with region faults. number of inputs to the system is relatively small, but too large to allow for exhaustive testing of every possible input to the  systems . It provides good test coverage with test cases.

13. 5. Syntax Driven Testing Very good methodology for compliers and parsers. Use BNF notation. Described by grammar. Grammar for simple arithmetic: (exp)::=(exp)+(term)|(exp)-(term)|(term) (term)::=(term)*(factor)|(term)-(factor)|(factor) (factor)::=(identifier)|(<expression>) (id)::=| a|b|c|d|e ………|z

14. 6. Decision Table-Based Testing A  decision table  is a good way to deal with combinations of things (e.g. inputs). This technique is sometimes also referred to as a ’cause-effect’ table. The reason for this is that there is an associated logic diagramming technique called ’cause-effect graphing’ which was sometimes used to help derive the decision table 

15. Conditions                      Rule 1                 Rule 2                Rule 3               Rule 4 Repayment amount has been entered: Term of loan has been Entered: Empty decision table:

16. 7. Cause and Effect Graphs in Functional Testing Represents relationship between input and output Input  cause Output  effect. Ex: ATM Banking Transaction System

17. Causes: C1: Command is credit C2: Command is Debit C3: Account Number is valid. C4: Transaction amount is Valid. Effects: E1: Print “Invalid command” E2: Print “invalid account number” E3: Print “debit amount not valid” E4: debit account E5: credit account.

18. Types processing modes And  effect occurs of all the inputs are true. Or  Effect occurs if at least one input is true Negation : effect occurs if input are false.

19. C2 C3 C4 E3 and Used to reduce the test case count C1 C2 C3 C4 Don’t care condition false True