Software Quality AssuranceBlack Box

Seminar: Oana FEIDIQuality Manager – Continental Automotive

Previewthe problem …

very large or infinite number of test scenarios+

finite amount of time=

impossible to test everything

the solution …Software test techniques exist to reduce

the number of tests to be run whilst still providing sufficient coverage of the system under test

OverviewBlack-box testing:

Test cases derived from specifications The focus is not the design, nor the

implementation

positive testing → testing the implementation against specified conditions

negative testing → testing the implementation against unspecified conditions (unspecified inputs)→ stability and robustness of specifications

Input Output

Equivalence partition

create partitions of the input and output values of the component

each partition shall contain a set or range of values, chosen such that all values can reasonably expected to be treated by the component in the same way

both valid and invalid values are partitioned in this way

For each test case specify: Input to the component Partition exercised The expected outcome of the test case

Test completeness criteria: test at least one input/output pair for each equivalence partition

Indicates when to stop testing

Equivalence partition

Example: f(int month) – want to test this function

…, -1, 0, 1, 2, 3, …., 9, 10, 11, 12, 13, 14, ….______||____________________||__________ invalid1 valid partition invalid2

f(int month, int nrdays) – want to test this function1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑31 28/29 31 30 31 30 31 31 30 31 30 31

Valid partition: [(1, 3, 5, 7, 8, 10, 12; 31), (4, 6, 9, 11; 30), …] Invalid partition: [(1, 2, 3, 5, 7, 8, 10, 12; 30), …]

Boundary Analysis

refinement of equivalence partitioning for which each edge of an equivalence class is a representative element of the class

invalid-input elements are found just beyond the ends

For each test case specify: the input(s) to the component the partition boundaries exercised The expected outcome of the test case

Test completeness criteria: test at least one input/output pair for each equivalence partition and the “borders” between the equivalence partitions

Boundary Analysis

Example: f(int month) – want to test this function

if (month > 0 && month < 13) or

if (month >= 0 && month < 13)

…, -1, 0, | 1, 2, 3, …., 9, 10, 11, 12 |, 13, 14, ….

|_________________________|valid partition

Test: 0, 1, 12, 13

Exercise 1 Use equivalence partition and boundary analysis

techniques to identify the values that have to be tested for the following parameters

State Transition Testing use a model of the states the component may

occupy, transitions between those states, the events which cause those transitions, and the actions which may result from those transitions

the model shall comprise states, transitions, events, actions and their relationships

For each test case specify: the starting state of the component the input(s) to the component the expected outputs from the component the expected final state

Test completeness criteria: 100% of the state transition diagram

State Transition Testing

Exercise 2

State 1

Dim

State 2

ON

State 3

OFF

State 0

Voltage

1) E1/A1 or2) E5/A1

E3E7

E8

1) E4(C1) or2) E10(C1) or3) E2(C1) or

4) E9(C1)

1) E1/A1 or2) E5(C1)/A1

E6/A2

(C2)

/A

3

default

Identify the paths using the state transition techniques

Condition DescriptionC1 All doors are closedC2 Duty cycle>51

Action DescriptionA1 Turn IL onA2 Turn IL offA3 Decrement duty cycle by

DIMM_STEP_INTERIOR_LIGHT_TIME every 20 ms

Event DescriptionE1 At least one of the driver door, assistant

door or trunk is openE2 A lock request is issuedE3 Duty cycle from PWM = 51E4 SHORT_INTERIOR_LIGHT_TIME expiredE5 An unlock request is issuedE6 CONTIN_INTERIOR_LIGHT_TIME expiredE7 Voltage failure flag is setE8 Voltage failure flag is not setE9 IGN is onE10 UNLOCK_INTERIOR_LIGHT_TIME expired

State DescriptionState 0: Voltage Voltage failure flag is set, IL is OFFState 1: Dim IL is dimmingState 2: ON IL is onState 3: OFF IL is off

Black Box - summary Equivalence partition

create partitions of the input and output values of the component each partition shall contain a set or range of values, chosen such

that all values can reasonably expected to be treated by the component in the same way

both valid and invalid values are partitioned in this way

Boundary Analysis refinement of equivalence partitioning for which each edge of an

equivalence class is a representative element of the class invalid-input elements are found just beyond the ends

State Transition Testing use a model of the states the component may occupy, transitions

between those states, the events which cause those transitions, and the actions which may result from those transitions

the model shall comprise states, transitions, events, actions and their relationships

Decision table Decision Table

A decision table is a tabular form that presents a set of conditions and their corresponding actions.

Condition Stubs Condition stubs describe the conditions or factors that will affect the

decision or policy. They are listed in the upper section of the decision table.

Action Stubs Action stubs describe, in the form of statements, the possible policy

actions or decisions. They are listed in the lower section of the decision table.

Rules Rules describe which actions are to be taken under a specific

combination of conditions. They are specified by first inserting different combinations of condition attribute values and then putting X's in the appropriate columns of the action section of the table.

Decision Table Methodology1. Identify Conditions & Values

Find the data attribute each condition tests and all of the attribute's values.

2. Compute Max Number of Rules

Multiply the number of values for each condition data attribute by each other.

3. Identify Possible Actions

Determine each independent action to be taken for the decision or policy.

4. Enter All Possible Rules

Fill in the values of the condition data attributes in each numbered rule column.

5. Define Actions for each Rule

For each rule, mark the appropriate actions with an X in the decision table.

6. Verify the Policy Review completed decision table with end-users.

7. Simplify the Table Eliminate and/or consolidate rules to reduce the number of columns.

Example

A marketing company wishes to construct a decision table to decide how to treat clients according to three characteristics: Gender, City Dweller, and age group: A (under 30), B (between 30 and 60), C (over 60). The company has four products (W, X, Y and Z) to test market.

Product W will appeal to female city dwellers. Product X will appeal to young females. Product Y will appeal to Male middle aged shoppers

who do not live in cities. Product Z will appeal to all but older females.

Example 1. Identify Conditions & Values

gender: M, F city dweller: Y, N age group: A, B, C

2. Compute Maximum Number of Rules: 2 x 2 x 3 = 12

3. Identify Possible Actions: market product W market product X market product Y market product Z

Example

4. Enter All Possible

Rules 1 2 3 4 5 6 7 8 9 10 11 12

Gender F M F M F M F M F M F M

City Y Y N N Y Y N N Y Y N N

Age A A A A B B B B C C C C

1 2 3 4 5 6 7 8 9 10 11 12

W X X X

X X X

Y X

Z X X X X X X X X X X

• 5. Define Actions for each Rule

Example Simplify the Table

◦ rules 2, 4, 6, 7, 10, 12 have the same action pattern ◦ rules 2, 6 and 10 have two of the three condition values (gender

and city dweller) identical and all three of the values of the non- identical value (age) are covered, so they can be condensed into a single column 2

◦ The rules 4 and 12 have identical action pattern, but they cannot be combined because the indifferent attribute "Age" does not have all its values covered in these two columns. Age group B is missing

Conditions

Gender F M F M F F M F F M

City Y Y N N Y N N Y N N

Age A - A A B B B C C C

Actions

W X X X

X X X

Y X

Z X X X X X X X X

1 2 3 4 5 6 7 8 9 10

Conclusions

Advantages of Black Box Testing more effective on larger units of code

than glass box testing tester needs no knowledge of

implementation, including specific programming languages

tester and programmer are independent of each other

tests are done from a user's point of view

will help to expose any ambiguities or inconsistencies in the specifications

test cases can be designed as soon as the specifications are complete

Conclusions

Disadvantages of Black Box Testing only a small number of possible inputs can

actually be tested, to test every possible input stream would take nearly forever

without clear and concise specifications, test cases are hard to design

there may be unnecessary repetition of test inputs if the tester is not informed of test cases the programmer has already tried

may leave many program paths untested cannot be directed toward specific segments of

code which may be very complex (and therefore more error prone)

most testing related research has been directed toward glass box testing

THANK YOU!