09_Functional_Testing.ppt

COMP 6710 Course NotesSlide 9-1Auburn UniversityComputer Science and Software Engineering

Course Notes Set 9:

Functional Testing

Computer Science and Software EngineeringAuburn University


• 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

Functional Testing


• Test-to-pass

- make sure the software minimally works- don’t push it to the limit- apply simplest and/or straightforward cases- not to find bugs, initially- do this test FIRST

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

Purpose of Testing


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.


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]


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


Equivalence Partitioning

• It is impossible to test all cases• Equivalence partitioning provides a systematic means

for selecting cases that matter and ignoring those that don’t

• 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 >= 15 then do-this else do-that

(- 15) 15 (15 )



• 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



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 => may not reveal all catchable bugs



• 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]


Example

Ï¬¹¹¹¹¹¹¹¹¹Þßàfunction in_list (input1:name_type;Ï§ÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏÏinput_list : list_names)Ï§Ïreturn boolean isÏªË¹¹¹¹¹¹¹¹ÏÏ§ÏíÏp : list_names;ÏÏ§beginÏÏ¨¹¹Ïp := input_list;ÏÏ¨¹¹±while not(p = null) loopÏÏ§ÏÏ·¹³´if Ada.Strings.Fixed.Index ÏÏ§ÏÏ¯Ïµ§(Source => String(p.name),ÏÏ§ÏÏ¯Ïµ§Pattern => String(input1)) /= 0 then ÏÂÄÏÏ¯Ïµ¾¹¹Ïreturn true;ÏÏ§ÏÏ¯Ï¶´else ÏÏ§ÏÏ¯Ï¸¾¹¹Ïp := p.next_name;ÏÏ§ÏÏ¯ÏÈÏend if;ÏÏ§ÏÏ°end loop;ÏÂÄ¹¹Ïreturn false;

Equivalence Classes:(1) Inputs where input1 is in the list

(2) Inputs where input1 is not in the list

Specific Input Partitions:List input1Empty ?One element In the listOne element Not in the list>One element First element>One element Last element>One element Middle element>One element Not in list

Test CasesList input1 Output<nil> ? falsebird bird truebird fish falsebird, cat, owl bird truedog, pig, chicken chicken true

...


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

( ))( (


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)



• Boundary conditions for a legitimate triangle

• Boundary conditions for side classification

• Boundary conditions for angle classification

• Valid input/extremes



• Types of Boundary conditionsnumeric character position quantityspeed location size

Also, extremes

first/last min/max start/finish over/underempty/full Shortest/longest slowest/fastest

largest/smallest …



• 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


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


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)


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}

x y z

A

B


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”


MFP for the Triangle Problem

Acute Obtuse Right

Scalene

Isosceles

Equilateral

Additional Functional Test Cases (if any):


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


Cause-Effect Graph Symbology

Identity

“Not”

“And”

“Or”

Symbology Constraints

c1

c1

c1

c2

c1

c2

e1

e1

e1

e1

c

a

a

a

a a

b

b

b

b b

E I O

R M

ExclusiveInclusive

Only One

Requires Masks


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”


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


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


Complete Cause-Effect Graphc1

c2

c3

c4

c5

c6

c8

c7

c9

i1

i2

i3

e1

e2

e3

e4


Converting to a Decision Table

1 2 3 4 5 6 7 8 9 10 11

c1c2

c3c4c5

c6c7c8

c9

e1e2e3e4

I = invoked A = absentS = suppressed P = presentX = don't care

09_Functional_Testing.ppt

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