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Lecture 19: Structural Testing
Kenneth M. Anderson
Software Methods and Tools
CSCI 3308 - Fall Semester, 2003
(Happy Halloween!)
October 31, 2003
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Today’s Lecture^ ^
Discuss Structural Testing^
Terminology Techniques Examples
October 31, 2003
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3
Structural Testing^ ^
Structural Testing supplies another criteria to answerthe question:^
“How many test cases are enough?” ^
Recall that functional testing’s criteria was “Test allfunctions” ^
Structural Testing’s criteria is “Test all code”^
Structural Testing is also known as white box testing,because now we look at a program’s source code to helpcreate test cases
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Control Flow Graphs (CFGs)^ ^
Structural Testing is based on CFGs
^
Control flow graphs capture the various waysin which a program can execute^
A node in a CFG represents a program statement An edge in the CFG represents the ability for aprogram to flow from its current statement to thestatement at the other end of the edge
^
If an edge is associated with a conditional, label the edgewith the conditional’s value, either true or false
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5
(^123456789101112131415)
function
P
return
INTEGER
is
begin
X, Y: INTEGER;READ(X); READ(Y); while
(X > 10)
loop
X := X – 10; exit when
X = 10;
end loop
;
if^ (Y < 20
and then
X
mod
2 = 0)
then
Y := Y + 20; else
Y := Y – 20; end if
; return
^2
∗^
X^ +
Y;
end
P;
A Sample Ada Program
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T^
T F
F^
T
F
T
F
P’s Control Flow Graph (CFG)
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7
Types of Coverage^ ^
Statement Coverage^ ^
Every statement is executed at least once
^
Edge Coverage^ ^
Every edge is traversed at least once
^
Condition Coverage^ ^
For binary logical operators (&&, ||), the individual components areevaluated in every possible combination of true and false
^
Relational Coverage^ ^
For relational operators (<, >, <=, >=) the equal condition is treated as aseparate branch
^
Path Coverage^ ^
Every possible path is executed at least once
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White-box Testing Criteria^ ^
Statement Coverage^
Execute each statement at least once Pick test case and plot its path through theCFG Keep picking test cases until all statementsare covered
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13
White-box Testing Criteria^ ^
Edge Coverage^
Traverse each edge at least once Pick test case and plot its path through CFG Keep picking test cases until all edges arecovered ^
Also known as Branch Coverage^
We must traverse each conditional (such as an ifstatement) along its true and false edge
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All-Edges Coverage of P 2,3,
T^
T F
F^
T
F
T
F
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15
Test Case 1: X = 20, Y = 10 2,3,
T^
T F
F^
T
F
T
F
Example all-edges-adequate test set:
(X = 20, Y = 10)
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Test Case 2: X = 15, Y = 30 2,3,
T^
T F
F^
T
F
T
F
Example all-edges-adequate test set:
(X = 20, Y = 10)(X =15, Y = 30)
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17
Combined: Complete Coverage 2,3,
T^
T F
F^
T
F
T
F
Example all-edges-adequate test set:
(X = 20, Y = 10)(X =15, Y = 30)
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White-box Testing Criteria^ ^
Condition Coverage^
Traverse all edges at least once but
^
in binary logical operators (also known as shortcircuit operators), all possible combinations oftrue and false must be tested
^
Pick test case and plot its path throughCFG; keep creating test cases until allconditions are covered
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19
All-Conditions Coverage of P 2,3,
T^
T F
F^
T
F
T
F
October 31, 2003
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Test Case 1: X = 20, Y = 10 2,3,
T^
T F
F^
T
F
T
F
Example all-conditions-adequate test set:
(X = 20, Y = 10)
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25
Relational Coverage, continued^ ^
Relational coverage is thus a stronger form ofedge coverage
^
It is saying that for each conditional youshould have at least three test cases^
x < y, x > y, x == y ^
Combine this approach with conditionalcoverage and you have the strongest form ofedge coverage possible
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Path Coverage^ ^
Path Coverage^
Traverse each path at least once ^
Problem^
Way too many paths, even in simple programs ^
Approach^
Use heuristics
^
e.g. for each loop take loop zero, one, and multiple times
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27
Example^ ^
How many paths does thefollowing program fragmenthave?^ a << cin; b = 0;while (a > 0) {
a--; b++; } if (b > 5) {
printf(“b > 5”); } else {
printf(“b <= 5”); }
^
For any particular valueof a, there is only onepath possible ^
but since a is enteredby user, there are aninfinite number ofpossible paths!
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Path Coverage, continued^ ^
In general^ ^
for loops^
traversing a loop zero, one, two, … times is each a differentpath, so a loop has a potentially infinite number of paths ^
for conditionals^
traverse true and false branches for a program consisting of only if statements
^
if x is the number of if statements, there are a total of 2
x^ paths!
^
As such, path coverage is an infeasible testingcriteria in the general case; so use heuristics toapproximate it, as discussed previously
