Course Notes Set 9: Functional Testing

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Course Notes Set 9Functional Testing

• Computer Science and Software Engineering
• Auburn University

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Functional Testing

• Dynamic (running) black-box (blindfolded) testing
• Also known as behavioral testing
• Based on specification
• - if one not available, the software is the spec
• Exam inputs/outputs needs test cases

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Purpose of Testing

• Test-to-pass
• - make sure the software minimally works
• - dont push it to the limit
• - apply simplest and/or straightforward cases
• - not to find bugs, initially
• - do this test FIRST

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Purpose of Testing

• Test-to-fail
• - after test-to-pass
• - design and run test cases with the purpose
• to break the software
• - probe the known and unknown weaknesses
• - errors forcing

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Functional (Black Box) Testing

• Knowing the specified function (requirements),
  design test cases to ensure that those
  requirements are met.
• Example Sort (list)
• Structural Testing - How well is the code
  exercised?
• Functional Testing - How well does Sort perform
  its intended function?
• In general, complete functional testing is not
  feasible
• Attempting to test every possible input to the
  function
• A randomly selected set of test cases is
  statistically insignificant
• Not all test cases are created equally
• Test case selection
• Based on characteristics of input and output sets
  relative to specified functionality.

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Functional Testing

• Types of errors looked for during functional
  testing
• Incorrect function or missing function
• Interface errors
• External database errors
• Performance errors (including stress testing)
• Initialization/termination errors
• Tests are designed to answer the following
  questions
• How is functional validity tested?
• What classes of input will make good test cases?
• Is the system particularly sensitive to certain
  input values?
• How are the boundaries of a data class isolated?
• What data rates and data volume can the system
  tolerate?
• What effect will specific combinations of data
  have on system operations?

Adapted from Software Engineering 4th Ed, by
Pressman, McGraw-Hill, 1997
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Goals and Methods of Functional Testing

• Goals
• Produce test cases that reduce the overall number
  of test cases
• Generate test cases that will tell us something
  about the presence or absence of errors for an
  entire class of input
• Methods/Approaches
• Equivalence partitioning
• Boundary value analysis
• Matrix of functional possibilities
• Cause-effect graphing
• Decision Tables

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Equivalence Partitioning

• It is impossible to test all cases
• Equivalence partitioning provides a systematic
  means for selecting cases that matter and
  ignoring those that dont
• An equivalence class or equivalence partition is
  a set of test cases that tests the same aspect or
  reveals the same bugs
• e.g., If X gt 15 then do-this else do-that
• (-? 15) 15 (15 ?)

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Equivalence Partitioning

• Equivalence partitions groups for similar
  inputs, outputs, and/or operation of the software
• e.g., file-name, 1 .. 255 characters
• - valid characters
• - invalid characters
• - valid length
• - invalid length

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Equivalence Partitioning

• e.g., copy operation
• - copy menu
• - c or C
• - Ctrl-c or Ctrl-Shift-c
• Fully tested in the first effort, equivalence
  partitioning (1 case each) test for new versions
• Goal to reduce the set of possible test cases
• Too few partitions gt may not reveal all
  catchable bugs

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Equivalence Partitioning

• Equivalence partitioning divides the input domain
  of a program into classes of data from which test
  cases can be derived
• Ideally, each test case could uncover classes of
  errors, thereby reducing the total number of test
  cases that must be developed
• Input condition - some kind of condition placed
  on the input
• Typically a specific value, a range of values, a
  set of related values, or a Boolean condition
• Equivalence Class - a set of valid or invalid
  states for input conditions
• Range - 1 valid and 2 invalid equivalence classes
  are defined
• Specific Value - 1 valid and 2 invalid
  equivalence classes are defined
• Set - 1 valid and 1 invalid equivalence class are
  defined
• Boolean - 1 valid and 1 invalid equivalence class
  are defined

Adapted from Software Engineering 4th Ed, by
Pressman, McGraw-Hill, 1997
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Example
Equivalence Classes (1) Inputs where input1 is
in the list (2) Inputs where input1 is not in
the list Specific Input Partitions List input1
Empty ? One element In the list One element Not
in the list gtOne element First element gtOne
element Last element gtOne element Middle
element gtOne element Not in list Test
Cases List input1 Output ltnilgt ? false bird bir
d true bird fish false bird, cat,
owl bird true dog, pig, chicken chicken true ...
Ϲ¹¹¹¹¹¹¹¹ Þßàfunction in_list
(input1name_type ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏinput_list
list_names) ÏÏreturn boolean
is Ϫ˹¹¹¹¹¹¹¹ ÏÏÏíÏp list_names ÏÏbegin ÏϹ
¹Ïp input_list ÏϹ¹while not(p null)
loop ÏÏÏϹ³if Ada.Strings.Fixed.Index
ÏÏÏÏϵ(Source gt String(p.name), ÏÏÏÏϵPat
tern gt String(input1)) / 0 then
ÏÂÄÏÏϵ¾¹¹Ïreturn true ÏÏÏÏÏelse
ÏÏÏÏϾ¹¹Ïp p.next_name ÏÏÏÏÏÈÏend
if ÏÏÏÏend loop ÏÂĹ¹Ïreturn false
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Boundary Value Analysis

• Range a..b
• Example 100..200
• Test cases 99, 100, 101, 199, 200, 201
• Number of values
• Test cases that exercise minimums and maximums
• Apply the above to the output conditions
• Try to drive output to invalid range
• Internal data structures with boundaries
• Example A(1..100) with test cases A(0), A(1),
  A(2), A(99), A(100), A(101)
• A(0) and A(101) should generate exceptions

(
(
(
)
)
a
b
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Boundary Condition Test Cases

• If software can operate on the edge of its
  capabilities, it will almost certainly operate
  well under normal conditions
• For I 1 to 10
• data (I) -1
• end
• 10 elements, data(0), data(1), data(2)
• data(9), data(10), data(11)

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Boundary Condition Test Cases

• Boundary conditions for a legitimate triangle
• Boundary conditions for side classification
• Boundary conditions for angle classification
• Valid input/extremes

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Boundary Condition Test Cases

• Types of Boundary conditions
• numeric character position quantity
• speed location size
• Also, extremes
• first/last min/max start/finish over/under
• empty/full Shortest/longest slowest/fastest large
  st/smallest

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Boundary Condition Test Cases

• Partitions
• - boundary
• - one or two valid points inside the boundary
• - one or two invalid points outside the
• boundary
• e.g., First 1 / Last 1
• Smallest 1 / Largest 1

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Sub-boundary Conditions

• Also known as Internal boundaries
• Bit, nibble, byte, word, K, M, G, T
• Why? E.g., 256 commands, 15 are frequently
• used. Needs only a nibble.
• ? 0XXXX nibble, 1XXXXXXXX byte

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Sub-boundary Conditions

• ASCCI table boundaries not obvious
• Default, empty, blank, null, zero, none
• (may be of a separate equivalence partition
• and treated individually)
• Invalid, wrong, incorrect, garbage data
• (test to fail)

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Matrix of Functional Possibilities

• Input/Output Conditions
• If the number of combinations of input/output is
  manageable, then consider using a matrix of
  functional possibilities
• Especially useful if the input/output
  combinations are enumerated in the requirements
  specification
• Example Input (or output) will be a combination
  of A,B and x,y,z

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Example The Triangle Problem

• Input
• 3 floating point numbers
• Processing
• Determine if the 3 numbers form a triangle
• If not, print message Not a Triangle
• If it is a triangle
• Classify according to side equilateral,
  isosceles, scalene
• Classify according to largest angle acute,
  right, obtuse
• Output
• List the 3 numbers
• List the classification or Not a triangle

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MFP for the Triangle Problem
Additional Functional Test Cases (if any)
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Cause Effect Graphing

• Causes (input conditions) and effects (actions)
  are listed for a module, and an identifier is
  assigned to each
• A cause-effect graph is developed
• Looking for causes without effects
• Looking for effects without causes
• The graph is converted to a decision table (if a
  decision table has been used as a design tool,
  developing the graph and table is not necessary)
• Decision table rules are converted to test cases

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Cause-Effect Graph Symbology
Symbology
Constraints
Identity
e1
c1
a
a
a
E
b
I
O
Not
c1
e1
b
b
c
Exclusive
Only One
c1
Inclusive
And
e1
c2
a
a
R
M
c1
b
b
Or
e1
Requires
Masks
c2
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Cause-Effect Graphing Example

• The CHANGE subcommand - used to modify a
  character string in the current line of the
  file being edited
• Inputs
• Syntax C /string1/string2
• String1 represents the character string you wish
  to replace
• 1-30 characters
• Any character except /
• String2 represents the character string that is
  to replace string1
• 0-30 characters
• Any character except /
• At least one blank must follow the command name
  C

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Cause-Effect Graphing Example

• Outputs
• Changed line is printed to the terminal if the
  command is successful
• NOT FOUND is printed if string1 cannot be found
• INVALID SYNTAX is printed if the command syntax
  is incorrect
• System Transformations
• If the syntax is valid and string1 can be found
  in the current line, then string1 is removed and
  string2 replaces it
• If the syntax is invalid or string1 cannot be
  found, the line is not changed

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Cause-Effect Graphing Example

• Cause 1 The first nonblank character following
  the C and one or more blanks is a /
• Cause 2 The command contains exactly two /
  characters
• Cause 3 String1 has length 1
• Cause 4 String1 has length 30
• Cause 5 String1 has length 2-29
• Cause 6 String2 has length 0
• Cause 7 String2 has length 30
• Cause 8 String2 has length 1-29
• Cause 9 The current line contains an occurrence
  of string1
• Effect 1 The changed line is typed
• Effect 2 The first occurrence of string1 in the
  current line is replaced by string2
• Effect 3 NOT FOUND is printed
• Effect 4 INVALID SYNTAX is printed

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Complete Cause-Effect Graph
c1
e1
c2
c3
i1
c4
e2
i3
c5
c6
e3
c7
i2
c8
c9
e4
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Converting to a Decision Table