White-Box Testing

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White-Box Testing

• Pfleeger, S. Software Engineering Theory and
  Practice 2nd Edition. Prentice Hall, 2001.
• Ghezzi, C. et al., Fundamentals of Software
  Engineering. Prentice Hall, 2002.
• Pressman, R., Software Engineering A
  Practitioners Approach, Mc Graw Hill, 2005.

1209
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White Box Testing

• Also known as
• Glass box testing
• Structural testing
• Test set is derived from structure of code
• Code structure represented as a Control Flow
  Graph
• Goal is to cover the CFG

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Control Flow Graphs

• Programs are made of three kinds of statements

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Control Flow Graph (CFG)
Sequence
If-then-else
Iterative
If-then
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Example 1 CFG
1. read (result) 2. read (x,k) 3. while
result lt 0 then 4. ptr ? false 5. if x gt k
then 6. ptr ? true 7. x ? x 1 8.
result ? result 1 9. print result
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Write a CFG

• Example 2
• 1. if (a lt b) then
• 2. while (a lt n)
• 3. a ? a 1
• 4. else
• 5. while (b lt n)
• 6. b ? b 1

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Answers

• Example 3
• 1. read (a,b)
• 2. if (a ? 0 b ? 0) then
• 3. c ? a b
• 4. if c gt 10 then
• 5. c ? max
• else c ? min
• 7. else print Done

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Answers

• Example 4
• 1. read (a,b)
• 2. if (a ? 0 b ? 0) then
• 3. c ? a b
• 4. while( c lt 100)
• 5. c ? a b
• 6. c ? a b

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Cyclomatic Complexity

• Software metric for the logical complexity of a
  program.
• Defines the number of independent paths in the
  basis set of a program
• Provides the upper bound for the number of tests
  that must be conducted to ensure that all
  statements been have executed at least once
• For Edges (E) and Nodes (N)
• V(G) E N 2

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Complexity of CFGs
3,4
3,4
1
1
5
5
6
2
Join
Join
3
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Example
1
2,3
6
4,5
8
7
9
10
11
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Example 1 CFG
1,2
3
9
4,5
6
Join
7,8
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Example 2
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Answers
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Answers
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Criteria

• Statement coverage
• Branch coverage
• Condition coverage
• (lots of others )

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Branch Coverage

• Each edge of a programs CFG is traversed at
  least once in some test.
• Independent paths
• 1, 2, 3, 9
• 1, 2, 3, 4, 5, 6, 7, 8, 3, , 9
• 1, 2, 3, 4, 5, 7, 8, 3, , 9

Example 1
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Criteria

• Statement coverage
• Branch coverage
• Condition coverage
• Every complex condition is made true and false by
  every possible combination
• E.G., (x and y)
• x true, y true
• xfalse, ytrue
• x true, y false
• x false, y false

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AND Condition
1, 2A
2B
4
3
Join
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OR Condition
1,2A
3
2B
4
5
Join
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Path Coverage-1

• Every distinct path through code is executed at
  least once
• Basis set does not yield minimal test set
• Example
• 1. read (x)
• 2. read (z)
• 3. if x ? 0 then begin
• 4. y ? x z
• 5. x ? z end
• 6. else print Invalid
• 7. if y gt 1 then
• 8. print y
• 9. else print Invalid
• Test Paths
• 1, 2, 3, 4, 5, J1, 7, 8, J2
• 1, 2, 3, 4, 5, J1, 7, 9, J2
• 1, 2, 3, 6, J1, 7, 8, J2,
• 1, 2, 3, 6, J1, 7, 9, J2

1,2,3
4,5
6
Join1
7
8
9
Join2
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Def-Use Coverage

• Def-use coverage every path from every
  definition of every variable to every use of that
  definition is exercised in some test.
• Example
• 1. read (x)
• 2. read (z)
• 3. if x ? 0 then begin
• 4. y ? x z
• 5. x ? z end
• 6. else print Invalid
• 7. if y gt 1 then
• 8. print y
• 9. else print Invalid

Def x, z Use x
1,2,3
4,5
Def y, x Use x, z
6
Use none
Join
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Use y
8
Use none
9
Use y

• Test Path 1, 2, 3, 4, 5, 7, 8, J

Join
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Strength of Coverage
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What paths dont tell you

• Timing errors
• Unanticipated error conditions
• User interface inconsistency (or anything else)
• Configuration errors
• Capacity errors