BLACK – BOX TESTING

Black box testing attempt to final errors in the following categories:1. I correct or missing Fns2. Interface errors.3. Errors in data structures or external data base access.4. Behavior or performance errors.5. Initialization and termination errors

I Graph Based Testing:First step in black box testing is to understand the objects that are modeled in s/w and the relationships that connect their object. Testing begins with creating a graph of imp. Objects and their relationship and then devising a series of tests that will cover the graph so that each object and relationship is exercised and errors are uncovered.We start with creating a graph

Directed link ----> relations bet. ObjectsNode weight ----> attributes of the objects.Nodes ----> Objects.Graph based testing begins with the defn of all nodes and node weights. ie, objects and attributes are identified. The data model can be used as a starting point.Based on this, we can conduct the following behavioral testing methods: Transaction flow modelling Finite state modeling Data flow modeling.Now we must go for node coverage and link coverages to ensure that all objects and their relations are executed.

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II Equivalence partitioning:Here the ip domain is divided in to classes of data from which test cases can be derived. An ideal test case is one which single – handedly uncovers a class of errors. If the ip class defines a range, one valid and two invalid classes are defined. If an ip cond,n req. a spec. value, one valid and two invalid equivalence classes are defined. If an ip condn specifies a member of set. One valid and one invalid equivalence class are defined. If an ip cond’n is one valid and one invalid class are defined.III Boundary Value Analysis :Boundary value analysis leads to a selection of teat cases that exercise bounding values. BVA leads to the selection of test cases at the edges of the class. BVA derives test cases from the output domain. If ip specifies a range of values bounded by a & b, then test cases should be designed with values a and b and just above and below a and b. Test care should be designed to create an op report that produces the max (win) allowable no. of table entries.III Boundary Value Analysis : (Back – to – back)And when the reliability of the s/w is very critical. In such situations, redundant s/w and L/W are used to minimize the possibility of error. When redundant s/w is dev, sep. s/w engg. Teams dev. independent versions of an applies using the same spec. In such cases each version can be tested with the same test data to ensure that all provide identical output.If the op from each version is the same, it is assumed that all implementations are correct. If the op is different, each of the applies is investigated to det. if a defect is one or more versions is responsible for the difference.If the spec. from which all versions have been dev. is in error. If each of there versions will provide identical but incorrect results, condn’s testing will fail to detect the error.