decision table-based testing - york university · dtt–44 decision table - equivalence class...
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Decision Table-Based Testing
Chapter 7
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Introductory question
What is a decision table? A simple non-technical answer?
A detailed technical answer?
DTT–2
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DTT–3
Decision Tables - Wikipedia
A precise yet compact way to model complicated logic
Associate conditions with actions to perform
Can associate many independent conditions with severalactions in an elegant way
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DTT–4
Decision Table Terminology
Stub Rule 1 Rule 2 Rules3,4
Rule 5 Rule 6 Rules7,8
c1 T T T F F Fc2 T T F T T Fc3 T F - T F -a1 X X Xa2 X Xa3 X Xa4 X X
condition stubs condition entriesaction stubs action entries
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DTT–5
Decision Table Terminology – 2
condition stubs condition entriesaction stubs action entries
What is a limited entry decision table?
What is an extended entry decision table?
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DTT–6
Decision Table Terminology – 3
condition stubs condition entriesaction stubs action entries
Limited entry table Condition entries restricted to binary values
Extended entry table Condition entries have more than two values
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DTT–7
Printer Troubleshooting DT
Conditions
Printer does not print Y Y Y Y N N N N
A red light is flashing Y Y N N Y Y N N
Printer is unrecognized Y N Y N Y N Y N
Actions
Check the power cable X
Check the printer-computercable X X
Ensure printer software isinstalled X X X X
Check/replace ink X X X X
Check for paper jam X X
A complete limited entry table
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DTT–8
DT Interpretation – Conditions
How are condition entries in a decision tableinterpreted with respect to a program?
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DTT–9
DT Interpretation – Conditions – 2
Conditions are interpreted as
Input
Equivalence classes of inputs
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DTT–10
DT Interpretation – Action entries
How are action entries in a decision tableinterpreted with respect to a program?
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DTT–11
DT Interpretation – Action entries – 2
Actions are interpreted as
Output
Major functional processing portions
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DTT–12
DT and test cases
What is the relationship between decision tablesand test cases?
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DTT–13
DT and test cases – 2
What is the relationship between decision tablesand test cases? Each rule in a decision table gives a test cases
With a complete decision table Have based on the decision structure of the
program A complete set of test cases
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DTT–14
Triangle Decision Table
C1: <a, b,c > forms a triangle? F T T T T T T T T
C3: a = b? – T T T T F F F F
C4: a = c? – T T F F T T F F
C5: b = c? – T F T F T F T F
A1: Not a Triangle X
A2: Scalene X
A3: Isosceles X X X
A4: Equilateral X
A5: Impossible X X X
Action added by a tester showing impossible rules
1 2 3 4 5 6 7 8 9
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DTT–15
Triangle Decision Table – refined
C1-1: a < b+c? F T T T T T T T T T T
C1-2: b < a+c? – F T T T T T T T T T
C1-3: c < a+b? – – F T T T T T T T T
C2: a = b? – – – T T T T F F F F
C3: a = c? – – – T T F F T T F F
C4: b = c? – – – T F T F T F T F
A1: Not a Triangle X X X
A2: Scalene X
A3: Isosceles X X X
A4: Equilateral X
A5: Impossible X X X
Similar to equivalence classes we can refine the conditions
1 2 3 4 5 6 7 8 9 10 11
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DTT–16
Triangle Test Cases
Case ID a b c Expected Output1 4 1 2 Not a Triangle
2 1 4 2 Not a Triangle
3 1 2 4 Not a Triangle
4 5 5 5 Equilateral
5 ??? ??? ??? Impossible
6 ??? ??? ??? Impossible
7 2 2 3 Isosceles
8 ??? ??? ??? Impossible
9 2 3 2 Isosceles
10 3 2 2 Isosceles
11 3 4 5 Scalene
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Exercise – Admission to University
Students in The range [80%, 100%] gpa are admitted and receive a
scholarship.
The range [70%, 80%) gpa are admitted but have noscholarship.
The range [60%, 70%) gpa are admitted if they have nofailures.
Otherwise they are not admitted.
DTT–17
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Good night for Leila – Program
arrive_at_dormitory(0)
arrive_at_dormitory(ask_counter)L: if Saturday night then if likes boy then if asked in last five minutes then ask_counter++ if ask_counter ≠ 3 then goto L else dispense good-night kiss fi fi fi fi say good night end
DTT–18
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Good night for Leila – DT
DTT–19
Saturday night Y Y Y Y N
Likes boy Y Y Y N –
Asked within 5 minutes Y Y N – –
Ask count = 3 Y N – – –
Dispense kiss X
Say good night X X X X
Repeat X
Exit X X X X
1 2 3 4 5
DTs have other constructs in additionto repeat and exit
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DTT–20
NextDate Decision Table
The NextDate problem illustrates the correspondencebetween equivalence classes and decision table structure
The NextDate problem illustrates the problem ofdependencies in the input domain
Decision tables can highlight such dependencies
Impossible dates can be clearly marked as a separateaction
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DTT–21
NextDate Equivalence Classes – for 1st try
M1 = {month : 1 .. 12 | days(month) = 30 }
M2 = {month : 1 .. 12 | days(month) = 31 }
M3 = {month : {2} }
D1 = {day : 1 .. 28}
D2 = {day : {29} }
D3 = {day : {30} }
D4 = {day : {31} }
Y1 = {year : 1812 .. 2012 | leap_year (year) }
Y2 = {year : 1812 .. 2012 | common_year (year) }
As in discussion forequivalence classes
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DTT–22
NextDate Decision Table – mutually exclusive conditions
C1: month in M1? T – –
C2: month in M2? – T –
C3: month in M3? – – T
A1: Impossible
A2: Next Date
Because a month is an equivalence classwe cannot have T for more than one entry.The do not care entries are really F.
Other problems?
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DTT–23
NextDate DT (1st try - partial)
C1: month in M1? T T T T T T T T
C2: month in M2? T T T T
C3: month in M3?
C4: day in D1? T T T T
C5: day in D2? T T T T
C6: day in D3? T T
C7: day in D4? T T
C8: year in Y1? T T T T T T
C9: year in Y2? T T T T T T
A1: Impossible X X
A2: Next Date X X X X X X X X X X
How many rules• for a complete table?• with don't care entries?
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Rule count – limited entry tables
How many rules are in a complete limited entrytable?
DTT–24
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DTT–25
Rule count – limited entry tables – 2
How many rules are in a complete limited entrytable?
Limited entry tables with N conditions have 2N rules.
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DTT–26
Rule count – limited entry with don't care entries
Don't care entries reduce the number of explicit rules byimplying the existence of non-explicitly stated rules.
How do you compute the number of rules a tablecontains including all the implicit rules due to don'tcare entries?
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DTT–27
Rule count – limited entry with don't care entries – 2
How do you compute the number of rules a tablecontains including all the implicit rules due to don'tcare entries?
Each don't care entry in a rule doubles the count forthe rule
For each rule determine the corresponding rule count
Total the rule counts
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DTT–28
Rule count – limited entry with don't care entries – 3
C1-1: a < b+c? F T T T T T T T T T T
C1-2: b < a+c? – F T T T T T T T T T
C1-3: c < a+b? – – F T T T T T T T T
C2: a = b? – – – T T T T F F F F
C3: a = c? – – – T T F F T T F F
C4: b = c? – – – T F T F T F T F
Rule count 32 16 8 1 1 1 1 1 1 1 1 +/ = 64
= 26
123456
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DTT–29
Rule count – Extended entry table
How many rules in a complete extended entry table withno don't care entries?
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DTT–30
Rule count – Extended entry table – 2
How many rules in a complete extended entry table withno don't care entries?
× / [[ c : 1..#conditions • number_of_values_for (c) ]]
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DTT–31
Rule count – Extended entry table – 3
How do you compute the number of rules a tablecontains including all the implicit rules due to don'tcare entries?
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DTT–32
Rule count – Extended entry table – 4
How do you compute the number of rules a tablecontains including all the implicit rules due to don'tcare entries?
Each don't care entry in a rule multiplies the countfor the rule by the number of values for thecorresponding condition
For each rule determine the corresponding rule count
Total the rule counts
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DTT–33
Rule count usefulness
Is it useful to count the rules in a decision table?
Why?
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Rule count usefulness – 2
Less rules than combination rule count
Indicates missing rules
More rules than combination rule count
Could indicate redundant rules See Table 7.9, page 107
Could indicate inconsistent table See Table 7.10, page 108
DTT–34
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DTT–35
NextDate Equivalence Classes – for 2nd try
M1 = {month : 1 .. 12 | days(month) = 30 }
M2 = {month : 1 .. 12 | days(month) = 31 }
M3 = {month : {2} }
D1 = {day : 1 .. 28}
D2 = {day : {29} }
D3 = {day : {30} }
D4 = {day : {31} }
Y1 = {year : {2000} }
Y2 = {year : 1812 .. 2012 | leap_year (year) ∧ year ≠ 2000 }
Y3 = {year : 1812 .. 2012 | common_year (year) }
Handle leap year better
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DTT–36
NextDate DT (2nd try - part 1)
C1: month in M1 M1 M1 M1 M2 M2 M2 M2
C2: day in D1 D2 D3 D4 D1 D2 D3 D4
C3: year in – – – – – – – –
A1: Impossible X
A2: Increment day X X X X X
A3: Reset day X X
A4: Increment month X ???
A5: reset month ???
A6: Increment year ???
Extended entry table – more refined actions
This table has 16 rules. How many rules for a complete table?
1 2 3 4 5 6 7 8
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DTT–37
NextDate DT (2nd try - part 2)
C1: month in M3 M3 M3 M3 M3 M3 M3 M3
C2: day in D1 D1 D1 D2 D2 D2 D3 D3
C3: year in Y1 Y2 Y3 Y1 Y2 Y3 – –
A1: Impossible X X X X
A2: Increment day X
A3: Reset day X X X
A4: Increment month X X X
A5: reset month
A6: Increment year
9 10 11 12 13 14 15 16
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DTT–38
New Equivalence Classes – for 3rd try
M1 = {month : 1 .. 12 | days(month) = 30 }
M2 = {month : 1 .. 12 | days(month) = 31 ∧ month ≠ 12 }
M3 = {month : {12} }
M4 = {month : {2} }
D1 = {day : 1 .. 27}
D2 = {day : {28} }
D3 = {day : {29} }
D4 = {day : {30} }
D5 = {day : {31} }
Y1 = {year : 1812 .. 2012 | leap_year (year) }
Y2 = {year : 1812 .. 2012 | common_year (year) }
Handle end of month andyear better
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DTT–39
NextDate DT (3rd try - part 1)
C1: month in M1 M1 M1 M1 M1 M2 M2 M2 M2 M2
C2: day in D1 D2 D3 D4 D5 D1 D2 D3 D4 D5
C3: year in – – – – – – – – – –
A1: Impossible X
A2: Increment day X X X X X X X
A3: Reset day X X
A4: Increment month X X
A5: reset month
A6: Increment year
A 22 rule table
1 2 3 4 5 6 7 8 9 10
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DTT–40
NextDate DT (3rd try - part 2)
C1: month in M3 M3 M3 M3 M3 M4 M4 M4 M4 M4 M4 M4
C2: day in D1 D2 D3 D4 D5 D1 D2 D2 D3 D3 D4 D5
C3: year in – – – – – – Y1 Y2 Y1 Y2 – –
A1: Impossible X X X
A2: Increment day X X X X X X
A3: Reset day X X X
A4: Increment month X X
A5: reset month X
A6: Increment year X
11 12 13 14 15 16 17 18 19 20 21 22
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DTT–41
Decision Table - Equivalence Class Comparison
It has been shown that equivalence classes and decisiontables can be closely related.
What benefit do we get from using equivalenceclasses in place of decision tables?
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DTT–42
Decision Table - Equivalence Class Comparison – 2
It has been shown that equivalence classes and decisiontables can be closely related.
What benefit do we get from using equivalenceclasses in place of decision tables?
In problems with little decision logic Commission problem
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DTT–43
Decision Table - Equivalence Class Comparison – 3
It has been shown that equivalence classes and decisiontables can be closely related. What benefit do we get from using decision tables in
place of equivalence classes?
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DTT–44
Decision Table - Equivalence Class Comparison – 4
It has been shown that equivalence classes and decisiontables can be closely related. What benefit do we get from using decision tables in
place of equivalence classes? The idea of complete tables helps recognize the
occurrence of Redundancy Inconsistency
When a decision table and equivalence classes areequivalent
DT has fewer tests Can avoid meaningless tests cases Less impossible cases
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DTT–45
DT Applicability
When is a decision table method applicable?
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DTT–46
DT Applicability – 2
When is a decision table method applicable?
The specification is given or can be converted to adecision table .
The order in which the predicates are evaluated doesnot affect the interpretation of the rules or resultingaction.
The order of rule evaluation has no effect onresulting action .
Once a rule is satisfied and the action selected, noother rule need be examined.
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DTT–47
DT Applicability – #
The order of executing actions in a satisfied rule is ofno consequence.
The restrictions do not eliminate many applications.
In most applications, the order in which the predicatesare evaluated is immaterial.
Some specific ordering may be more efficient than someother but in general the ordering is not inherent in theprogram's logic.
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DTT–48
Decision Table Properties
You have constructed a decision table
Before deriving test cases, what properties shouldthe decision table have?
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DTT–49
Decision Tables Properties – 2
Before deriving test cases, ensure that
The rules are complete Every combination of predicate truth values is in the
decision table
The rules are consistent Every combination of predicate truth values results in
only one action or set of actions
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DTT–50
Guidelines and Observations
Decision Table testing is most appropriate for programswhere one or more conditions hold.
What are those conditions?
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DTT–51
Guidelines and Observations – 2
Decision Table testing is most appropriate for programswhere There is a lot of decision making
There are important logical relationships amonginput variables
There are calculations involving subsets of inputvariables
There is complex computation logic High cyclomatic complexity
There are cause and effect relationships betweeninput and output – ???
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DTT–52
Guidelines and Observations – 3
What are some problems with using decision tables?
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DTT–53
Guidelines and Observations – 4
Decision tables do not scale up very well May need to
Use extended entry decision tables Algebraically simplify tables
Decision tables need to be iteratively refined The first attempt may be far from satisfactory
Similar to using equivalence classes
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DTT–54
Guidelines and Observations – 5
Look for redundant rules More rules than combination count of conditions Actions are the same Too many test cases See Table 7.9, page 107
Look for inconsistent rules More rules than combination count of conditions Actions are different for the same conditions See Table 7.10, page 108
Look for Missing rules Incomplete table