april 1,200291.3913 r mcfadyen1 a traditional software development process unit test integration...

April 1,2002 91.3913 R McFadyen 1

A Traditional Software Development Process

Unit test

Integration test

System test

Detailed design

Architectural design

Analysis

Requirements analysis

Business modeling process

Business results


Black Team

Peopleware: Productive Projects and Teams

by Tom Demarco and Timothy Lister

Ch 19: The Black Team

•"legendary" Black Team at IBM in 60’s

•a particularly effective testing team

•the best testers at the company

•testers delighted in finding new ways to break software

•programmers dreaded having their software go through Black Team testing

•promoted themselves by dressing all in black

•the spirit of the Black Team has survived


Testing

Unit testing •Equivalence classes•Boundary classes•Black-box testing•White-box testing

Integration testing

System testing

Object-oriented testing


Black-box Testing

• A blackbox test is one that focuses on the input/output behaviour of a component without considering its implementation

• The system being tested is a black box, whose behaviour is determined by studying its inputs and outputs

• aka functional testing since it is concerned with functionality and not implementation

• Equivalence testing

• Boundary testing


Equivalence testing

• A technique to minimize the number of test cases• An equivalence class is a set of tests with common characteristics• A test case is selected for each class• We use our domain knowledge to generate equivalence classes• example: suppose a method returns the number of days in a

month, given the month and year.– When we consider months, we could arrive at 3 equivalence

classes:• months with 31 days• months with 30 days• months with 28 or 29 days

– When we consider years, we have two equivalence classes: leap years and non-leap years

– Combining, we have 6 equivalence classes


Six equivalence classes

Equivalence classInput values

month year

31 day month, non-leap year 7 1901

31 day month, leap year 7 1904



28/29 day month, non-leap year 2 1901

28/29 day month, leap year 2 1904


Boundary testing

•We focus on the boundary conditions of equivalence classes

•Rather than selecting any element in an equivalence class, boundary testing requires that elements be selected from the “edges”

Example

•In general, years that are multiples of 4 are leap years; years that are multiples of 100 are not leap years, unless they are multiples of 400.

•2000 is a leap year, but 1900 is not

•For Year, 2000 and 1900 are good boundary cases

•0 and 13 would be good boundary cases for month


Ten equivalence classes

Equivalence classInput values

month year31 day month, non-leap year 7 1901




28/29 day month, non-leap year 2 1901

28/29 day month, leap year 2 1904

Leap year divisible by 400 2 2000

Non-leap year divisible by 100 2 1900

Non-positive invalid month 0 1904

positive invalid month 13 1904


Whitebox testing

Boundary and Equivalence testing: if you know the algorithm, you will be able to generate more test classes.

Path testing: A whitebox testing technique based on flow of control

•Construct a flow graph for Cyclomatic Complexity

•The minimum number of tests necessary to cover all edges is the number of independent paths through the flow graph

•Design test cases such that each transition is traversed at least once - examine each condition and select an input for the true branch and another for the false branch


public class MonthOutOfBounds extends Exception {…};public class YearOutOfBounds extends Exception {…};

class MyGregorianCalendar {public static boolean isLeapYear(int year) {boolean leap;if (year%4) {

leap = true;} else {

leap = false;}return leap;

}

public static int getNumDaysInMonth(int month, int year)...

A (faulty) Java implementation of getNumDaysInMonth()

See next slide

What’s wrong here?


public static int getNumDaysInMonth(int month, int year) throws MonthOutOfBounds, YearOutOfBounds {

int numDays;if (year < 1) {

throw new YearOutOfBounds(year);}if (month==1 || month==3 || month==5 || month==7 || month==10 || month==12) {

numDays = 32;} else if (month==4 || month==6 || month==9 || month==11) {

numDays = 30;} else if (month == 2) {

if (isLeapYear(year)) {numDays = 29;

} else {

numDays = 28;}

} else {

throw new MonthOutOfBounds(month);}

return numDays;}

...}

What’s wrong here?


Flow graph - as a UML activity diagram

year out of bounds

month out of bounds

n = 32

n = 30

n = 28

n = 29

[year < 1]

[month in {1,3,5,7,10,12}]

[month in {4,6,9,11}]

[month=2][leap year]


UML activity diagram (flow graph)

year out of bounds

month out of bounds

n = 32

n = 30

n = 28

n = 29

[year < 1]

[month in {1,3,5,7,10,12}]

[month in {4,6,9,11}]


1

2

3

4

5 6

We can walk through the flow graph and generate 6 tests to ensure each transition is traversed


UML activity diagram (flow graph)

year out of bounds

month out of bounds

n = 32

n = 30

n = 28

n = 29

[year < 1]

[month in {1,3,5,7,10,12}]

[month in {4,6,9,11}]


1

2

3

4

5 6

We can walk through the flow graph and generate 6 tests to ensure each transition is traversed

Year=0; month=7

Year=1999; month=7

Year=1999; month=6

Year=2000; month=2

Year=1999; month=2

Year=2000; month=0


What is the flow graph for isLeapYear()?

What tests can we generate from it?

isLeapYear()

Which tests, of all the tests we’ve outlined, will actually help us find the problems with these two methods?


Another White-box Testing Example

FindMean(float Mean, FILE ScoreFile) …

What is the flow graph for FindMean?

What is the CC?

What tests can we generate from the CC … to know all paths have been executed?


/*Read in and sum the scores*/

Another White-box Testing Example

FindMean(float Mean, FILE ScoreFile)

{ SumOfScores = 0.0; NumberOfScores = 0; Mean = 0;

Read(ScoreFile, Score);

while (! EOF(ScoreFile) {

if ( Score > 0.0 ) {

SumOfScores = SumOfScores + Score;

NumberOfScores++;

}

Read(ScoreFile, Score);

}

/* Compute the mean and print the result */

if (NumberOfScores > 0 ) {

Mean = SumOfScores/NumberOfScores;

printf("The mean score is %f \n", Mean);

} else

printf("No scores found in file\n");

}


Prepare for Flow Graph

FindMean (FILE ScoreFile){ float SumOfScores = 0.0;

int NumberOfScores = 0; float Mean=0.0; float Score;Read(ScoreFile, Score);while (! EOF(ScoreFile) {

if (Score > 0.0 ) {SumOfScores = SumOfScores + Score;NumberOfScores++;}

Read(ScoreFile, Score);}/* Compute the mean and print the result */if (NumberOfScores > 0) {

Mean = SumOfScores / NumberOfScores;printf(“ The mean score is %f\n”, Mean);

} elseprintf (“No scores found in file\n”);

}

1

2

3

4

5

7

6

89


Constructing the Logic Flow Diagram

4

3

2

1

5

6

7 8

9

CC = 11-9+2 = 4

1, 2, 6, 8, 9

1, 2, 6, 7, 9 is not possible

1, 2, 3, 4, 5, 2, 6, 7, 9

1, 2, 3, 4, 5, 2, 6, 8, 9 is not possible

1, 2, 3, 5, 2, 6, 8, 9

1, 2, 3, 5, 2, 6, 7, 9 is not possible

ok

ok

ok

Note: If node 4 is included then node 7 must be included

These 3 tests cover all paths! We didn’t need 4!


Testing

Testing tools can count the number of times instructions are executed. This is examined for completeness – that all paths have been executed.

How would knowledge of the algorithm (the code) affect your choices of equivalence classes and boundary classes?

• Suppose you are testing a search method. What equivalence and boundary classes would you decide on?

• Suppose you know the search is a binary search and not a simple selection search … this should affect your classes


Class model for a testing system?

is caused by

* *

Test case

Failure FaultError

Test suite

is caused by

*

*

CorrectionComponent

Test stub

Test driver

exercises is revised by

finds repairs

*

* *

*

* * 1…n

*

*


Testing

Example:

Suppose we have a search module to test. We know:

– the list, elt, must have at least one element

– if the element, key, is found, found will be true and elt[L] = key

– if the key is not found, found will be false

How do we structure, or organize, our test cases?


Black-box Testing

Example (continued):• How do we structure, or organize, our test cases?

• We have two types of searches: successful and unsuccessful. So, we can partition our search test cases into two classifications: found and not found

• When it comes to lists of elements, we know that lists of length 1, are special cases or boundary points. So, we should have 2 partitions of lists: length 1, and length of more than one.

• When an element is searched for, it can be found in boundary positions. So, we can should have 3 partitions: found at the start, found at the end, and then we should include where it is found in the middle.


Black-box Testing

Found Not Found

List of 1 element List of 1 element

Example (continued):•combining the partitions

List of >1 element

In 1st position

In last position

In middle position

List of >1 element

1 2

3

4

5

6


Black-box Testing

55

44

Example (continued):•sample tests for the 6 partitions

55 33 88 44

22 33 6 77 88 44

33 66 77 88 22

22 55 88 66 77

1

2

3

4

5

6

55 true, 1

55 false, ?

55 true, 1

44 true, 6

77 true, 3

99 false, ?

Outputs Found, L

Inputs List Key


White-box Testing

•Tests are derived from knowledge of the software’s construction

•aka structural, glass-box, or clear-box testing

•Tester analyzes the code, the algorithm, to derive test data


White-box Testing

Example:

suppose we are examining an algorithm that searches an ordered list for a specific value in Key.

•On examination we see it’s a binary search and we see that it really treats the List as having 3 sections:

elements < midmid-point

elements > mid


White-box Testing

•:We can use this knowledge to further refine our partitioning - we need to test for where the Key we are looking for is at the boundary points for these partitions.

elements < midmid-point

elements > mid

We’ll add two more tests


White-box Testing

Example:

55

44

55 66 77 88 99

22 33 44 50 56 61 76

22 33 44 50 56 61 76

22 33 44 50 56 61 76

1

2

3

4

5

6

55 true, 1

55 false, ?

55 true, 1

50 true, 4

76 true, 7

44 true, 3

Outputs Found, L

Inputs List Key

22 33 44 50 56 61 767 56 true, 522 55 88 66 778 99 false, ?


Integration Testing

Combine components into a systemTypical strategy is bottom-up or top-down• Top-down

– related to top-down development– development starts with high-level components and

works down. – Incomplete modules are stubs with the interface, but

little or no functionality.– As top level is programmed and tested, the sub-

components are implemented and tested, …• Bottom-up

– ... (requires more test drivers)• Big-bang … difficult to pinpoint errors


Object-Oriented Integration Testing

Class testing• more than one method/operation• statechart diagrams

• transitions … events that can cause a change in state must be tested

Subclasses•Subclasses should be tested for inherited operations•Overridden operations must be tested

Integration testing (top? bottom?)•Collaboration testing

•Test objects for support of system events and Use Cases •Test significant object collaborations•Note on page 311: suggests implementation from least-coupled to most-coupled


System Testing

Test all subsystems as a single systemPerformance testing

– Stress test– Volume test– Security test– Recovery test– …

Acceptance testing– Benchmark test for typical conditions– Shadow test– Installation test– Documentation test– …

april 1,200291.3913 r mcfadyen1 a traditional software development process unit test integration...

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