Decision-to-decision path
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A decision-to-decision path, or DD-path, is a path of execution (usually through a flow graph representing a program, such as a flow chart) between two decisions. More recent versions of the concept also include the decisions themselves in their own DD-paths.

Definition
Summarize
Perspective
In Huang's 1975 paper,[1] a decision-to-decision path is defined as path in a program's flowchart such that all the following hold (quoting from the paper):
- its first constituent edge emanates either from an entry node or a decision box;
- its last constituent edge terminates either at a decision box or at an exit node; and
- there are no decision boxes on the path except those at both ends
Jorgensen's more recent textbooks restate it in terms of a program's flow graph (called a "program graph" in that textbook).[2] First define some preliminary notions: chain and a maximal chain. A chain is defined as a path in which:
- initial and terminal nodes are distinct, and
- all interior nodes have in-degree = 1 and out-degree = 1.
A maximal chain is a chain that is not part of a bigger chain.
A DD-path is a set of nodes in a program graph such that one of the following holds (quoting and keeping Jorgensen's numbering, with comments added in parentheses):[2]
- It consists of a single node with in-degree = 0 (initial node)
- It consists of a single node with out-degree = 0 (terminal node)
- It consists of a single node with in-degree ≥ 2 or out-degree ≥ 2 (decision/merge points)
- It consists of a single node with in-degree = 1 and out-degree = 1
- It is a maximal chain of length ≥ 1.
According to Jorgensen (2013), in Great Britain and ISTQB literature, the same notion is called linear code sequence and jump (LCSAJ).[2][dubious – discuss]
Properties
From the latter definition (of Jorgensen) we can conclude the following:
- Every node on a flow graph of a program belongs to one DD-path.
- If the first node on a DD-path is traversed, then all other nodes on that path will also be traversed.
- The DD path graph is used to find independent path for testing.
- Every statement in the program has been executed at least once.
DD-path testing
According to Jorgensen's 2013 textbook, DD-path testing is the best known code-based testing method, incorporated in numerous commercial tools.[2]
DD-path testing is also called C2 testing or branch coverage.[3][4]
See also
- Basic block
- Basis path testing and its ancillary articles
- Code coverage
- White-box testing
References
External links
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