What is Structural Testing?

Size: px

Start display at page:

Download "What is Structural Testing?"

Mercy Chase
5 years ago
Views:

1 Structural Testing

2 What is Structural Testing? Based on Source Code Examine the internal structure of the program Test cases are derived from an examination of program s logic Do not pay any attention to specification. The knowledge to the internal structure of code can be used to find the number of test cases required to guarantee a given level of test coverage.

3 Why Structural Testing is Required? Part of code not fully exercised. Section of code may be surplus to the requirements. Errors may be missed by functional requirements.

4 Levels of Coverage 1. Statement (Line) coverage 2. Decision (Branch) coverage 3. Condition coverage 4. Decision/Condition coverage 5. Multiple Condition coverage 6. Loop coverage 7. Path coverage

5 Levels of Coverage Statement Coverage

6 Levels of Coverage Branch Coverage

7 Levels of Coverage Branch Coverage

8 Levels of Coverage Condition Coverage Condition coverage reports the true or false outcome of each boolean sub-expression, separated by logical-and and logical-or if they occur. Condition coverage measures the sub-expressions independently of each other.

9 Levels of Coverage Decision/Condition Coverage A hybrid metric composed by the union of condition coverage and decision coverage

10 Levels of Coverage Levels of Coverage Multiple Condition Coverage

11 Levels of Coverage Loop Coverage This metric reports whether you executed each loop body zero times, exactly once, and more than once.

12 Path Testing(1) Group of test techniques based on judicious selecting a set of test paths through the program Most applicable to new software for module testing or unit testing The effectiveness of path testing rapidly deteriorates as the size of the software under test increases.

13 Path Testing(2) This type of testing involves: Generating a set of paths that will cover every branch in the program. Finding the set of test cases that will execute every path in this set of program paths. Steps Involved in Path testing: Generate flow graph of a program. Generate DD path graph. Identify independent paths

14 Path Testing Flow Graph (1) Used to analysis the control flow of a program Definition: Given a program written in a programming language, its program graph is a directed graph in which nodes are statement fragments, and edges represent flow of control. If I and J are nodes in the program graph, an edge exists from node I to node J if the statement fragment corresponding to node J can be executed immediately after the statement fragment corresponding to node I.

15 Path Testing Flow Graph (2) Sequence If then else Repeat until loop While loop Case

16 Path Testing Flow Graph (3) Example: 1. Triangle (a, b, c: Integer): String 4 2. IsATriangle: Boolean 3. begin 4. if (a<=b+c 5 or b<=a+c 6or c<=b+c) 5. then IsATriangle := true 6. else IsATriangle 7:= false ; 7. if (IsATriangle) 8. then 9. if (a=b 9 and b=c) then return Equilateral 11. else if (a b and 12 a c and b c) 13. then return Scalene 14. else 13 return Equilateral 14 ; 15. else return Not a triangle ; 16. end begin 4. (a<=b+c or b<=a+c or c<=b+c)? yes no 5. IsATriangle := true 6. IsATriangle := false 7. IsATriangle? yes no 9. (a=b and b=c)? 15. Not a triangle yes no 10. Equilateral 12. (a b and a c and b c)? yes no 13. Scalene 14. Equilateral 16. end

17 Path Testing DD Path Graph (1) Decision to decision path graph. DD path graph is a directed graph in which nodes are sequences of statements and edges represent control flow between node. Used to find independent path

18 Path Testing DD Path Graph (2) A Example: 14 B C D E F G H I J K L

19 Path Testing Independent Path (1) An independent path is any path through the program that introduces at least one new set of processing statements or a new condition. When stated in terms of a flow graph, an independent path must move along at least one edge that has not been traversed before the path is defined.

20 Path Testing Independent Path (2) C A B Independent paths are: ABGOQRS E H D F G O ABGOPRS ABCDFGOQRS ABCDEFGOPRS J I L K M P Q ABGHIJNRS ABGHIKLNRS N R ABGHIKMNRS S

21 Path Testing Computation of cyclomatic complexity (1) Structural Complexity. Given by McCabe. Used to find number of independent paths through the program. Provides an upper bound on the number of tests that must be conducted to ensure that all statements have been executed at lest once.

22 Path Testing Computation of cyclomatic complexity (2) Cyclomatic complexity has a foundation in graph theory and is computed in the following ways: 1. V(G) = E N + 2P E: number of edges N: number of nodes 2. V(G) = P + 1 P: number of predicate nodes 3. V(G)= number of region

23 Path Testing Computation of cyclomatic complexity (3) 1. V(G)= E N+2=? 2. V(G)= P + 1=? 3. V(G)= No regions=?

24 Path Testing Example Consider the program for the classification of a triangle (pages 399) Compute cyclomatic complexity based on the graph that presented in page 401 Determine independent Generate test cases which are coverage independent path

25 Data Flow Testing (1) Data flow testing focuses on the points at which variables receive values and the points at which these values are used (or referenced). It detects improper use of data values due to coding errors.

26 Data Flow Testing (2) Flow graph used as basic for data flow testing Data flow analyses centered on a set of faults that are known as define/reference anomalies. A variable that is defined but never used (referenced) A variable that is used but never defined A variable that is defined twice before it is used

27 Data Flow Testing (3) Definitions The definitions refer to a program P that has a program graph G(P) and set of program variables V. The graph G(P) has a single entry node and a single exit node. The set of all paths in P is PATHS(P)

28 Data Flow Testing (3) Definitions DEF(v, n): node n in G(P) is a defining node of variable v in V, iff the value of variable v is defined at the statement fragment corresponding to node n. USE(v, n): node n in G(P) is a usage node of variable v in V, iff the value of variable v is used at the statement fragment corresponding to node n. du-path: a definition-use path (du-path) with respect to variable v is a path in PATH S(P) such that, for some v in V, there are defined and usage nodes DEF(v, m) and USE(v, n) such that m and n are initial and final nodes of the path. dc-path: a definition-clear path with respect to a variable v is a du-path with initial and final node such that no other node in the path is defining node of v.

29 Data Flow Testing (4) Steps for Data Flow Testing Draw the program Flow graph Find the DD path graph Prepare the table for Def/Use status of all variable Find all du-path Identify du-path that are not dc-path Generate test cases to test all du-path at least one. If we cannot test all du-paths, we have to test all du-paths that are not dc-path.

30 Data Flow Testing (5) Example Consider example 8.20 (page 411)

Software Testing. 1. Testing is the process of demonstrating that errors are not present.

Software Testing. 1. Testing is the process of demonstrating that errors are not present. What is Testing? Software Testing Many people understand many definitions of testing :. Testing is the process of demonstrating that errors are not present.. The purpose of testing is to show that a program