Topic: Equivalence partitioning

Message

Overview

Equivalence partitioning is a method for deriving test cases.  In this
method, classes of input conditions  called equivalence classes  are
identified such that each member of the class causes the same kind of
processing and output to occur. 
In this method, the tester identifies various equivalence classes for partitioning.  A class
is a set of input conditions that are is likely to be handled the same way
by the system.  If the system were to handle one case in the class
erroneously, it would handle all cases erroneously.

Contents:

Definition

The Theory

Black Box vs. White Box

Types of Equivalence Classes

Why Learn Equivalence Partitioning?

Designing Test Cases Using Equivalence Partitioning

Definition

			Equivalence partitioning is a software testing technique to minimize 
			number of permutation and combination of input data. In equivalence 
			partitioning, data is selected in such a way that it gives as many 
			different out put as possible with the minimal set of data. 

			If software behaves in an identical way for a set of value, then 
			the set is termed as equivalence class or a partition. It can be 
			assumed safely that functionality of the software will be same for 
			any data value from the equivalence class or partition. In 
			equivalence partitioning, input data is analyzed and divided into 
			equivalence classes which produces different output.  
Now, data from these classes can be representative of all the input values that 
your software expect. For equivalence classes, it can be assumed that software 
will behave in exactly same way for any data value from the same partition.
The Theory

The testing theory related to equivalence partitioning says that only 
		one test case of each partition is needed to evaluate the behaviour of 
		the program for the related partition. In other words it is sufficient 
		to select one test case out of each partition to check the behaviour of 
		the program. To use more or even all test cases of a partition will not 
		find new faults in the program. The values within one partition are 
		considered to be "equivalent." Thus the number of test cases can be 
		reduced considerably.

An additional effect by applying this technique is that you also find 
		the so called "dirty" test cases. An inexperienced tester may be tempted 
		to use as test cases the input data 1 to 12 for the month and forget to 
		select some out of the invalid partitions. This would lead to a huge 
		number of unnecessary test cases on the one hand, and a lack of test 
		cases for the dirty ranges on the other hand.
Types of Equivalence Classes

Continuous classes, or ranges of values, run from one point to 
			another, with no clear separations of values. An example is a 
			temperature range.

Discrete classes have clear separation of values. Discrete 
			classes are sets, or enumerations.
		Boolean classes are either true or false. Boolean classes only 
			have two values, either true or false, on or off, yes or no. An 
			example is whether a checkbox is checked or unchecked.

Why Learn Equivalence Partitioning?

Equivalence partitioning drastically cuts down the number of test cases
required to test a system reasonably.

It is an attempt to get a good
'hit rate', to find the most errors with the smallest number
of test cases.

Designing Test Cases Using Equivalence Partitioning

To use equivalence partitioning, you will need to perform two steps
		Identify the equivalence classes 
		Design test cases 

		STEP 1: IDENTIFY EQUIVALENCE CLASSES

		Take each 
		input condition described in the specification and derive at least two 
		equivalence classes for it. One class represents the set of cases which 
		satisfy the condition (the valid class) and one represents cases which 
		do not (the invalid class ) Following are some general guidelines for 
		identifying equivalence classes:

alue is input to the system and must be within a range of 
		values, identify one valid class inputs which are within the valid range 
		and two invalid equivalence classes inputs which are too low and inputs 
		which are too high. For example, if an item in inventory can have a 
		quantity of - 9999 to + 9999, identify the following classes: 1. one 
		valid class: (QTY is greater than or equal to -9999 and is less than or 
		equal to 9999). This is written as (- 9999 < = QTY < = 9999) 2. the 
		invalid class (QTY is less than -9999), also written as (QTY < -9999) 3. 
		the invalid class (QTY is greater than 9999) , also written as (QTY 
		>9999) 

		b) If the requirements state that the number of items input by 
		the system at some point must lie within a certain range, specify one 
		valid class where the number of inputs is within the valid range, one 
		invalid class where there are too few inputs and one invalid class where 
		there are, too many inputs. For example, specifications state that a 
		maximum of 4 purchase orders can be registered against anyone product. 
		The equivalence classes are : the valid equivalence class: (number of 
		purchase orders is greater than or equal to 1 and less than or equal to 
		4 , also written as (1 < = no. of purchase orders < = 4) the invalid 
		class (no. of purchase orders> 4) the invalid class (no. of purchase 
		orders < 1)

		c) If the requirements state that a particular input item 
		match one of a set of values and each case will be dealt with the same 
		way, identify a valid class for values in the set and one invalid class 
		representing values outside of the set. For example, if the requirements 
		state that a valid province code is ON, QU, and NB, then identify : the 
		valid class code is one of ON, QU, NB the invalid class code is not one 
		of ON, QU, NB

		d) If the requirements state that a particular input item 
		match one of a set of values and each case will be dealt with 
		differently, identify a valid equivalence class for each element and 
		only one invalid class for values outside the set. For example, if a 
		discount code must be input as P for preferred customer, R for standard 
		reduced rate, or N for none, and if each case is treated differently, 
		identify the valid class code = P the valid class code = R the valid 
		class code = N the invalid class code is not one of P, R, N 

		e) If you 
		think any elements of an equivalence class will be handled differently 
		than the others, divide the equivalence class to create an equivalence 
		class with only these elements and an equivalence class with none of 
		these elements. For example, a bank account balance may be from $0 up to 
		$ 1,000,000, and balances $ 1,000 or over are not subject to service 
		charges. Identify : the valid class: ($ 0 < = balance < $ 1,000) i.e., 
		balance is between 0 and $ 1,000 - not including $ 1,000 the valid 
		class: ($ 1, 000 < = balance < = $ 1,000,000 i.e., balance is between $ 
		1,000 and $1,000,000 inclusive the invalid class: (balance < $ 0) the 
		invalid class: (balance> $ 1,000,000)

		Equivalence partitioning drastically cuts down the number of test cases
 required to test a system reasonably.  It is an attempt to get a good
 'hit rate', to find the most errors with the smallest number
 of test cases.

Edited by Mithi25 - 01Aug2009 at 6:12am

Author	Message
Mithi25 Senior Member Joined: 23Jun2009 Online Status: Offline Posts: 288	Topic: Equivalence partitioning Posted: 01Aug2009 at 6:11am
	Overview Equivalence partitioning is a method for deriving test cases. In this method, classes of input conditions called equivalence classes are identified such that each member of the class causes the same kind of processing and output to occur. In this method, the tester identifies various equivalence classes for partitioning. A class is a set of input conditions that are is likely to be handled the same way by the system. If the system were to handle one case in the class erroneously, it would handle all cases erroneously. Contents: Definition The Theory Black Box vs. White Box Types of Equivalence Classes Why Learn Equivalence Partitioning? Designing Test Cases Using Equivalence Partitioning Definition Equivalence partitioning is a software testing technique to minimize number of permutation and combination of input data. In equivalence partitioning, data is selected in such a way that it gives as many different out put as possible with the minimal set of data. If software behaves in an identical way for a set of value, then the set is termed as equivalence class or a partition. It can be assumed safely that functionality of the software will be same for any data value from the equivalence class or partition. In equivalence partitioning, input data is analyzed and divided into equivalence classes which produces different output. Now, data from these classes can be representative of all the input values that your software expect. For equivalence classes, it can be assumed that software will behave in exactly same way for any data value from the same partition. The Theory The testing theory related to equivalence partitioning says that only one test case of each partition is needed to evaluate the behaviour of the program for the related partition. In other words it is sufficient to select one test case out of each partition to check the behaviour of the program. To use more or even all test cases of a partition will not find new faults in the program. The values within one partition are considered to be "equivalent." Thus the number of test cases can be reduced considerably. An additional effect by applying this technique is that you also find the so called "dirty" test cases. An inexperienced tester may be tempted to use as test cases the input data 1 to 12 for the month and forget to select some out of the invalid partitions. This would lead to a huge number of unnecessary test cases on the one hand, and a lack of test cases for the dirty ranges on the other hand. Types of Equivalence Classes Continuous classes, or ranges of values, run from one point to another, with no clear separations of values. An example is a temperature range. Discrete classes have clear separation of values. Discrete classes are sets, or enumerations. Boolean classes are either true or false. Boolean classes only have two values, either true or false, on or off, yes or no. An example is whether a checkbox is checked or unchecked. Why Learn Equivalence Partitioning? Equivalence partitioning drastically cuts down the number of test cases required to test a system reasonably. It is an attempt to get a good 'hit rate', to find the most errors with the smallest number of test cases. Designing Test Cases Using Equivalence Partitioning To use equivalence partitioning, you will need to perform two steps Identify the equivalence classes Design test cases STEP 1: IDENTIFY EQUIVALENCE CLASSES Take each input condition described in the specification and derive at least two equivalence classes for it. One class represents the set of cases which satisfy the condition (the valid class) and one represents cases which do not (the invalid class ) Following are some general guidelines for identifying equivalence classes: alue is input to the system and must be within a range of values, identify one valid class inputs which are within the valid range and two invalid equivalence classes inputs which are too low and inputs which are too high. For example, if an item in inventory can have a quantity of - 9999 to + 9999, identify the following classes: 1. one valid class: (QTY is greater than or equal to -9999 and is less than or equal to 9999). This is written as (- 9999 < = QTY < = 9999) 2. the invalid class (QTY is less than -9999), also written as (QTY < -9999) 3. the invalid class (QTY is greater than 9999) , also written as (QTY >9999) b) If the requirements state that the number of items input by the system at some point must lie within a certain range, specify one valid class where the number of inputs is within the valid range, one invalid class where there are too few inputs and one invalid class where there are, too many inputs. For example, specifications state that a maximum of 4 purchase orders can be registered against anyone product. The equivalence classes are : the valid equivalence class: (number of purchase orders is greater than or equal to 1 and less than or equal to 4 , also written as (1 < = no. of purchase orders < = 4) the invalid class (no. of purchase orders> 4) the invalid class (no. of purchase orders < 1) c) If the requirements state that a particular input item match one of a set of values and each case will be dealt with the same way, identify a valid class for values in the set and one invalid class representing values outside of the set. For example, if the requirements state that a valid province code is ON, QU, and NB, then identify : the valid class code is one of ON, QU, NB the invalid class code is not one of ON, QU, NB d) If the requirements state that a particular input item match one of a set of values and each case will be dealt with differently, identify a valid equivalence class for each element and only one invalid class for values outside the set. For example, if a discount code must be input as P for preferred customer, R for standard reduced rate, or N for none, and if each case is treated differently, identify the valid class code = P the valid class code = R the valid class code = N the invalid class code is not one of P, R, N e) If you think any elements of an equivalence class will be handled differently than the others, divide the equivalence class to create an equivalence class with only these elements and an equivalence class with none of these elements. For example, a bank account balance may be from $0 up to $ 1,000,000, and balances $ 1,000 or over are not subject to service charges. Identify : the valid class: ($ 0 < = balance < $ 1,000) i.e., balance is between 0 and $ 1,000 - not including $ 1,000 the valid class: ($ 1, 000 < = balance < = $ 1,000,000 i.e., balance is between $ 1,000 and $1,000,000 inclusive the invalid class: (balance < $ 0) the invalid class: (balance> $ 1,000,000) Equivalence partitioning drastically cuts down the number of test cases required to test a system reasonably. It is an attempt to get a good 'hit rate', to find the most errors with the smallest number of test cases. Edited by Mithi25 - 01Aug2009 at 6:12am
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