How to calculate Statement, Branch/Decision Coverage

How to calculate Statement, Branch/Decision Coverage

HOW TO CALCULATE STATEMENT, BRANCH/DECISION AND PATH COVERAGE FOR ISTQB EXAM PURPOSE

Statement Coverage: (Find shortest path such that all nodes are covered at-least once)

In this, the test case is executed in such a way that every node is traversed at-least once.

Branch/Decision Coverage: (Find shortest path such that all the Edges are covered at-least once)
Test coverage criteria requires enough test cases such that each condition in a decision
takes on all possible outcomes at least once, and each point of entry to a program or
subroutine is invoked at least once. That is, every branch (decision) taken each way,
true and false. It helps in validating all the branches in the code making sure that no
branch leads to abnormal behavior of the application.

Path Coverage:(Find all the paths from source to destination)

In this the test case is executed in such a way that every path is executed at least once.
All possible control paths taken, including all loop paths taken zero, once, and multiple
(ideally, maximum) items in path coverage technique, the test cases are prepared based
on the logical complexity measure of a procedural design. In this type of testing every
statement in the program is guaranteed to be executed at least one time. Flow Graph,
Cyclomatic Complexity and Graph Metrics are used to arrive at basis path
How to calculate Statement Coverage, Branch Coverage and Path Coverage?

Draw the flow in the following way-
 Nodes represent entries, exits, decisions and each statement of code.
 Edges represent non-branching and branching links between nodes.

Example:
Read P
Read Q
IF P+Q > 100 THEN
Print “Large”
ENDIF
If P > 50 THEN
Print “P Large”
ENDIF
Calculate statement coverage, branch coverage and path coverage.




The flow chart is-

Statement Coverage (SC):

To calculate Statement Coverage, find out the shortest number of paths following
which all the nodes will be covered. Here by traversing through path 1A-2C-3D-E-4G-5H all
the nodes are covered. So by traveling through only one path all the nodes 12345 are covered,
so the Statement coverage in this case is 1.

Branch Coverage (BC):

To calculate Branch Coverage, find out the minimum number of paths which will
ensure covering of all the edges. In this case there is no single path which will ensure coverage
of all the edges at one go. By following paths 1A-2C-3D-E-4G-5H, maximum numbers of
edges (A, C, D, E, G and H) are covered but edges B and F are left. To covers these edges we
can follow 1A-2B-E-4F. By the combining the above two paths we can ensure of traveling
through all the paths. Hence Branch Coverage is 2. The aim is to cover all possible true/false
decisions.
Path Coverage (PC):
Path Coverage ensures covering of all the paths from start to end.
All possible paths are-
1A-2B-E-4F
1A-2B-E-4G-5H
1A-2C-3D-E-4G-5H
1A-2C-3D-E-4F
So path coverage is 4.
Thus for the above example SC=1, BC=2 and PC=4.
Memorize these….
100% LCSAJ coverage will imply 100% Branch/Decision coverage
100% Path coverage will imply 100% Statement coverage
100% Branch/Decision coverage will imply 100% Statement coverage
100% Path coverage will imply 100% Branch/Decision coverage
Branch coverage and Decision coverage are same.

Thanks,

Mohit Bhatia