UNIT TESTING. Plan project Integrate & test system Analyze requirements Design Maintain Test units...

UNIT TESTING

Plan project

Integrate & test system

Analyze requirements

Design

Maintain

Test unitsImplement

Software Engineering Roadmap

Identify corporate practices

Test units (parts) separately - use implementations - apply discipline - gain coverage

Adapted from Software Engineering: An Object-Oriented Perspective by Eric J. Braude (Wiley 2001), with permission.

Learning Goals

• Understand meaning of unit testing

• Distinguish black box vs. white box testing

• Attain proper test coverage

• Learn a testing standard

• Inspect a unit test plan


1. Introduction to unit testing

Golden Rules of Testing

Goal of testing: maximize the number and severity of

defects found per dollar spent … thus: test early

Limits of testing: Testing can only determine the

presence of defects, never their absence

– use proofs of correctness to establish “absence”

Who should test: Someone other than the developer.

– Why?


Testing: the Big Picture

Methods

Combinations of methods in class

Packages of classes

OO:

Include use-cases

Function

Module

Module combination

2. Integration tests

3.

System tests

1.Unittests

Elaboration

Unified Process

Inception Construction Transition

Requirements

Analysis

Design

Implemen-tation

Test

Jacobson et al: USDP

Prelim.iterations

Iter.#1

Iter.#n

Iter.#n+1

Iter.#m

Iter.#m+1

Iter.#k

….. …..

Unit Tests Integration tests ... System tests

RoadMap for Unit Testing

1. Plan for unit testing

Requirements

Unit test plan

2. Design test cases and acquire test I/O pairs

Generate I/O pairs (often products of prior testing)

3. Execute unit test

Test set

Test

results

Codeunder test

Detailed design

Identify largest trouble spots

IEEE, 1986

2. Test types

Black-, Gray-, & White-box Testing

Black box… requirements

Actual outputcompared

with required output

White box

Gray box… requirements &key design elements

Input determinedby...

Result

…designelements

Confirmationof expected

behavior

As for black- and white box

testing


Black-box testing

Equivalence Partitioning

• Input data and output results often fall into different classes where all members of a class are related

• Each of these classes is an equivalence partition where the program behaves in an equivalent way for each class member

• Test cases should be chosen from each partition

Equivalence Partitioning

Test Input Possibilities

interest rate0%

25%

principal

$100 $100M

inflation

estimate

1%

20%Infinitely many legal values:

choose a finite sample.

Infinitely many illegal values:

choose a finite sample.


Test Input Partitioning and Boundaries

interest rate0%

25%

principal

$100 $100M

inflation

estimate

Boundaries

1%

20%

Equivalence partitions

An illegal region

Range of valid inputs


Testing Ranges: Elementary Cases

1. within range

2. at the boundaries of the range

3. outside the range (“illegal”)

range


• Requirement: The system must accept a 5-digit integer between 10000 and 99999 and perform various functions on the values based on the following equivalence partitions:

<10000, 10000 - 99999 and >= 100000• Which test cases should be chosen?

Consider the boundaries of these sets …

00000, 09999, 10000, 99999, 100000, <max bin>

Equivalence Partitioning – Example

Equivalence Partitions

Between 10000 and 99999Less than 10000 More than 99999

999910000 50000

10000099999

Input values

White Box Testing

• Every statement of code should be covered by at least one test

• However, this is not sufficient since the correct opeation of a unit of code depends upon sequences of statements

Covering Every Statement is Not Sufficient (Myers)

u>1 andv==0

x = x/u

u==2 orx>0

++x

No

Yes

No

Yes

Required program

Covering Every Statement is Not Sufficient (Myers)

u>1 andv==0

x = x/u

u==2 orx>0

++x

No

Yes

Code attempt to implement flowchart

if( (u>1) && (v==0) ) (1)x = x/u; (2)

if( (u==2) || (x>3) ) (3)++x; (4)

u=2, v=0 and x=3 • executes every line (1) - (4) • gives the correct output x= 2.5 However, line (3) is wrongSO THIS IS NOT A THOROUGH TEST

No

Yes

Required program

Paths to be Checked

Parameter & settings make

sense?

Parameter name too

long?

N

YN

Set _name to “defaultName"

Y

Truncate name

Set _name to parameter

Paths to be Checked

Parameter & settings make

sense?

Parameter name too

long?

N

YN

Decision Coverage

Set _name to “defaultName"

Y

Truncate name

Set _name to parameter


Decision Coverage via Path testing

• The objective of path testing is to ensure that the set of test cases is such that each path through the program is executed at least once

• The starting point for path testing is a program flow graph that shows nodes representing program decisions and arcs representing the flow of control

• Statements with conditions are therefore nodes in the flow graph

• Describes the program control flow. Each branch is shown as a separate path and loops are shown by arrows looping back to the loop condition node

• Used as a basis for computing the cyclomatic complexity

• Cyclomatic complexity = Number of edges - Number of nodes +2

Program flow graphs

• The number of tests to test all control statements equals the cyclomatic complexity

• Cyclomatic complexity equals number of conditions in a program

• Useful if used with care. Does not imply adequacy of testing.

• Although all paths are executed, all combinations of paths are not executed

Cyclomatic complexity

Binary search (Java)

Binary search flow graph

• 1, 2, 3, 8, 9• 1, 2, 3, 4, 6, 7, 2• 1, 2, 3, 4, 5, 7, 2• 1, 2, 3, 4, 6, 7, 2, 8, 9• Test cases should be derived so that all of

these paths are executed• A dynamic program analyser may be used

to check that paths have been executed

Independent paths

Grey Box Testing

• Combination of Black and White box testing

Gray box… requirements &key design elements

Correct output and

expected behaviour

• Pre-conditions satisfied, key element in array• Pre-conditions satisfied, key element not in

array• Pre-conditions unsatisfied, key element in array• Pre-conditions unsatisfied, key element not in

array• Input array has a single value• Input array has an even number of values• Input array has an odd number of values

Grey Box Testing ExampleBinary search - equiv. partitions

Binary search equiv. partitions

Binary search - test cases

3. Planning unit tests

Plan for Unit Testing1. Decide on the philosophy for unit testing

– individual engineer responsible (common)? – reviewed by others?– designed & performed by others?

2. Decide what / where / how to document– individual’s personal document set (common)?– how / when to incorporate into other types of testing? – incorporate in formal documents?– use tools / test utilities?

3. Determine extent of unit testing (i.e., in advance).– do not just “test until time expires”– prioritize, so that important tests definitely performed

4. Decide how and where to get the test input5. Estimate the resources required

– use historical data if available6. Arrange to track time, defect count, type & source


4. Checklists and examples for Method testing

Perform Method Testing (Humphrey) 1/2

1. Verify operation at normal parameter values (a black box test based on the unit’s requirements)

2. Verify operation at limit parameter values(black box)

3. Verify operation outside parameter values(black box)

4. Ensure that all instructions execute (statement coverage)

5. Check all paths, including both sides of all branches (decision coverage)

6. Check the use of all called objects7. Verify the handling of all data structures8. Verify the handling of all files


Perform Method Testing (Humphrey) 2/2

9. Check normal termination of all loops

(part of a correctness proof)

10. Check abnormal termination of all loops

11. Check normal termination of all recursions

12. Check abnormal termination of all recursions

13. Verify the handling of all error conditions

14. Check timing and synchronization

15. Verify all hardware dependencies


5. Checklists and examples for class testing

1. Exercise methods in combination– 2-5, usually– choose most common sequences first– include sequences likely to cause defects– requires hand-computing the resulting attribute values

2. Focus unit tests on each attribute– initialize, then execute method sequences that affect it

3. Verify that each class invariant is unchanged– verify that the invariant is true with initial values– execute a sequence (e.g., the same as in 1.)– verify that the invariant still true

4. Verify that objects transition among expected states– plan the state / transition event sequence– set up the object in the initial state by setting variables– provide first event & check that transition occurred . etc.

Perform ClassUnit Tests


Encounter State-Transition Test Sequence 1 of 2

Waiting

Preparing

test step 1Verify that the game is initially in Preparing state (by checking on the class membership of gameStateI)

Player dismisses qualities

menu

Encounter State-Transition Test Sequence 1 of 2

Waiting

Preparing

test step 1test step 2

test step 3

Verify that the game is initially in Preparing state (by checking on the class membership of gameStateI)

Dismiss the quality menu, and verify that the game is in Waiting state.

Move the player character to an adjacent area, and verify that the game is still in Waiting state.


menu

Move to adjacent

area



menu

Character enters area

inhabited by an opponent

Move to adjacent

area

Complete Encounter State-Transition Test

Waiting

Preparing

Engaging

12

3

4

5

Reporting

Player dismisses encounter

report menu

Encounter completed

6


• Defect testing and debugging are distinct processes

• Inspection and testing is concerned with establishing the existence of defects in a program

• Debugging is concerned with locating and repairing these errors

• Debugging involves formulating a hypothesis about program behaviour then testing these hypotheses to find the error

Testing and debugging

The debugging process

UNIT TESTING. Plan project Integrate & test system Analyze requirements Design Maintain Test units...

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