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Wednesday, April 25, 2012

How does a definition clear path play a role in data flow testing?

Definition clear path is a quite less heard term! This article is focussed up on the concept of definition clear path and what role do it plays in the data flow testing. First let us define what is a definition clear path in actual. 

"A definition clear path as it can made out from the term itself that it is a path through which other variables cannot be defined or through which other variable definitions cannot be made."

To make the meaning of definition clear path clearer we shall look up to an example:
- Suppose X be a variable declared or appearing in a software program or procedure. 
- Suppose there is a path which do not contain any nodes with definition of the variable X.
- Such a path not containing any variable definitions has been termed as a definition clear path. 

We can now define this definition clear path as a path between the two nodes namely A and B, with X being defined in A and an use in node B and there exists no other definition of variable X between the two nodes present in the path. 

Let us see another example to explore another type of definition clear path that can exist. 
- Suppose the above same variable X be defined at a node A along with an use defined at the another node B.
- Suppose the path formed by these two nodes A and B does not appears in the sub path, then such a path is also defined as a definition clear path for the X variable defined by the nodes A and B if the variable X is not defined in the sub path. 
- There is another common name for the definition clear path which is “def- clear path”. 

Now let us talk about the role that the definition clear path plays in the data flow testing. Actually in the data flow testing, there are three types of coverage that have to be provided namely:
  1. Statement coverage
  2. Branch coverage and lastly
  3. Path coverage
Basically problems are faced with the path selection process. A definition of the variable X reaches a use if and only if there exists a sub path such that the sub path is a definition clear path with respect to the variable X. The path selection in the data flow testing is based up on the two criteria:

  1. Rapps and Weyuker criteria: Under these criteria the definition clear sub paths from definitions to uses are listed.
  2. Laski and Korel criteria: Under these criteria the various combinations that reach uses at a node via some sub path are listed.

How does Definition Clear Path play a role in Data Flow Testing?

- Definition clear paths have been known to make remarkable improvements in the control flow techniques for data flow testing.
- A rational is obtained for which there is a need to take in to consideration all the combinations of the sub paths. 
- The “all uses” is the most commonly preferred criteria.
- There are some paths in a program that are infeasible and it is these paths that pose a big problem in the data flow testing. 
- The path testing strategies are based up on the data flow anomalies. 
- Enough paths are required to be tested so that it is ensured that every object in the program has been initialized before use and have been used at least once during the program execution. 
- For a complete data flow testing it is required that definition clear paths are executed by the test cases from each node that contains a defined variable.

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