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Copyright PCSA, Inc Cis4932 (Dr. Ed Jones)

Florida A & M University Computer and Information Science e-learning

Testing of ClassesTesting of Classes



Testing of ClassesTesting of Classes

Features of classes:

•Attributes

•Behavior/Operations/Methods

•PRIVATE PART is INVISIBLE to the outside.



Testing of ClassesTesting of ClassesFeature of Classes• Attributes –

• private part • data describing an object• referred to as the STATE• Attribute values determine

BEHAVIOR,• i.e., how the methods react

to messages.

• Attributes – • private part • data describing an object• referred to as the STATE• Attribute values determine

BEHAVIOR,• i.e., how the methods react

to messages.



Testing of ClassesTesting of ClassesFeature of Classescontd

- Typically functions (methods) are for manipulating the object:

- Set operations -- store values into the state - Inquiry operations – return values of state variable(s)

Computation operations – perform computation using state

variable, without modifying state

variables. Transformational operations – modify state variables.

- Typically functions (methods) are for manipulating the object:

- Set operations -- store values into the state - Inquiry operations – return values of state variable(s)

Computation operations – perform computation using state

variable, without modifying state

variables. Transformational operations – modify state variables.

(2) Behavior/Operations/Methods:



Testing of ClassesTesting of Classes (3) PRIVATE PART is (3) PRIVATE PART is

INVISIBLE to the INVISIBLE to the outside.outside.

- Hard to verify effect

of certain public operations. -

Approaches: (1)Function-Driven. (Divide and Conquer).

Test each function (method). If each method works,

then the whole class must work.• - Use function testing techniques on each method

• Document test of each function



Testing of ClassesTesting of ClassesLimitations of Function-Driven approach

a)Class methods are not independent. Correctness of one requires

correctness of other methods. b) Order in which to test methods.c) Ability to test internal/private

functions.d)Ability to see the EFFECTS of a

function call, when there is an internal state change.



Testing of ClassesTesting of Classes (2) State-Driven.

(State = internal/private variables inside class).

-Identify relevant states (not every value of every variable is significant). -Ensure all state transitions have been exercised (state-transition coverage).



Testing of ClassesTesting of ClassesLimitations of State Driven approach

a) Hard to identify significant states

b)Must understand formal specification

using state models. c) Hard to get visibility into

current internal state.



Testing of ClassesTesting of Classes (3) Semantics/Usage-Driven

approach. (Semantics = the intended meaning/usage of

objects of a class type) Example: Stack rules. Push before Pop

Detection of empty/overflow. - Sequence

of calls to public methods required to DO A JOB

- valid and invalid sequences - Focus is on correct "external"

behavior



Testing of ClassesTesting of ClassesChallenge #1

Why this is important ? Testing requires

"finding" the results so that it can be compared to the expected result.

When the result is trapped inside an

object, one must be able to access it.

Why this is important ? Testing requires

"finding" the results so that it can be compared to the expected result.

When the result is trapped inside an

object, one must be able to access it.

Gaining access to the internal state



Testing of ClassesTesting of ClassesChallenge #1

contd

What is required The class must be modified temporarily to permit access

to the internal state. HOWEVER, the goal must be

to minimize the intrusiveness of such

modifications. Principle: If you modify what

you are testing, then you're not testing the original (real)

thing.

What is required The class must be modified temporarily to permit access

to the internal state. HOWEVER, the goal must be

to minimize the intrusiveness of such

modifications. Principle: If you modify what

you are testing, then you're not testing the original (real)

thing.



Testing of ClassesTesting of ClassesApproach to Gain Access to Internal State

1)Add "hooks" to the interface of the class

(public section)• - DATA TYPE:

struct instate declaring all the internal state variables

• - INQUIRY FUNCTIONS: a) Get_State (instate &) -- returns values of all state variables (contd)



Testing of ClassesTesting of ClassesApproach to Gain Access to Internal State

contd

- SET FUNCTIONS:- a) Set_State (instate &) -- set

state variables to the values contained in the state record being

passed.

- (2) LAST RESORT -- Make EVERYTHING PUBLIC.



Testing of ClassesTesting of ClassesCHALLENGE #2 -- Consolidating

the class test -

Challenge: A function-driven test mayrequire multiple drivers,one per function, along with tdi_ and trs_ and uts_ utl_ files. This creates a data management problem.Moreover, a function-driven test does not

address the overall behavior of the class.



Testing of ClassesTesting of ClassesCHALLENGE #2

-- Contd Strategy: Perform function-driven tests first.

NEXT apply usage- driven testing.

Strategy: Perform function-driven tests first. NEXT apply usage- driven testing.



Testing of ClassesTesting of ClassesApproach to challenge #2

-- Contd

APPROACH: (1) Usage-Driven class test driver

- menu driven based on inputs in tdi_ file: -- each menu selection identifies the class

method to be invoked. -- tdi_ file contains the "arguments“

needed for the call




-- Contd -- tdi_ file contains the expected results

• actual values • description of the effects

- A single trs_ file is producedtrs_ file echoes the tdi_ inputtrs_ file may contains resultsOr description of observed effects

Additional effort may be required to verify that all the expected effects occurred.




-- Contd

Identify user tasks (end-to-end) • Base tasks on the specification of the class • Base other tasks on "boundary conditions“

Identify the sequence of public operations required to perform the task.

APPROACH: 2) Usage-Driven Test Case Design



Testing of ClassesTesting of ClassesTable of Contents

Logic overview What is a proposition Proposition and logical operators

What are bit operators

NegationConjunctionDisjunctionExclusive ORImplication

Biconditional

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