Path Testing is a structural testing method based on the source code or algorithm and NOT based on the specifications. It can be applied at different levels of granularity.
The Specifications are Accurate
The Data is defined and accessed properly
There are no defects that exist in the system other than those that affect control flow
Control Flow Graph (CFG) - The Program is converted into Flow graphs by representing the code into nodes, regions and edges.
Decision to Decision path (D-D) - The CFG can be broken into various Decision to Decision paths and then collapsed into individual nodes.
Independent (basis) paths - Independent path is a path through a DD-path graph which cannot be reproduced from other paths by other methods.