Software-Testing-BVA

Study Notes - SOFTWARE TESTING of Maynooth Universtiy by Dr. Joe Timoney

Boundary Values Analysis

• ST ACTIVITIES

1. Analysis of SW / spec that informs the test
2. Identify test coverage items
3. Identify test cases
4. Verify test design to ensure completeness
5. Implementation of tests
6. Execution of tests
7. Examination of test results

EP design case - example

The bank customer enters how much money is deposited (represented as an integer) in a bank savings account. Based on the amount of money, the different interest rates are displayed:

a) 0.3% interest rate if the amount is between €1 and €100.

b) 0.5% interest rate if the amount is between €101 and €1000.

c) 0.7% interest rate if the amount is above €1000.

The initial balance of the account is €0 because of a lack of information. The deposited amount must be a positive number. Any error leads to a return value of 0.

1. Analysis of SW / spec that informs the test

Parameter	Minimum Value	Maximum Value
Deposit	Long.MIN_VALUE	0
	1	100
	101	1000
	1001	Long.MAX_VALUE

Return Value	0
	0.30%
	0.50%
	0.70%

2. Identify test coverage items

TCI	Parameter	Boundary Value	Test Case
BV1*	Deposit	Long.MIN_VALUE	To be completed later
BV2*		0
BV3		1
BV4		100
BV5		101
BV6		1000
BV7		1001
BV8		Long.MAX_VALUE
BV9	Return Value	0
BV10		0.30%
BV11		0.50%
BV12		0.70%

3. Identify test cases

ID	Test Cases Covered	Inputs Deposit	Exp. Result Return Value
T2.1	BV3,10	1	0.30%
T2.2	BV4,[10]	100	0.30%
T2.3	BV5,11	101	0.50%
T2.4	BV6,[11]	1000	0.50%
T2.5	BV7,12	1001	0.70%
T2.6	BV8,[12]	Long.MAX_VALUE	0.70%
T2.7	BV1*,9	Long.MIN_VALUE	0
T2.8	BV2*,[9]	0	0

4. Verify test design to ensure completeness

TCI	Parameter	Boundary Value	Test Case
BV1*	Deposit	Long.MIN_VALUE	T2.7
BV2*		0	T2.8
BV3		1	T2.1
BV4		100	T2.2
BV5		101	T2.3
BV6		1000	T2.4
BV7		1001	T2.5
BV8		Long.MAX_VALUE	T2.6
BV9	Return Value	0	T2.7
BV10		0.30%	T2.1
BV11		0.50%	T2.3
BV12		0.70%	T2.5

5. Implementation of tests

ID	Test Cases Covered	Inputs Deposit	Exp. Result Return Value
T2.1	BV3,10	1	0.30%
T2.2	BV4,[10]	100	0.30%
T2.3	BV5,11	101	0.50%
T2.4	BV6,[11]	1000	0.50%
T2.5	BV7,12	1001	0.70%
T2.6	BV8,[12]	Long.MAX_VALUE	0.70%
T2.7	BV1*,9	Long.MIN_VALUE	0
T2.8	BV2*,[9]	0	0

6. Execution of tests

Java + TestNG

Test automation with dataproviders

package trade_test_BVA;

import org.testng.annotations.Test;
import static org.testng.Assert.assertEquals;
import org.testng.annotations.DataProvider;

public class InterestCalculatorTest {

	// test data
	private static Object[][] testData = new Object[][] {
			// id, variable1, variable2, ... variableN, expected
		    {"T2.1",				    1,		 0.003},
	            {"T2.2",  	 			  100, 		 0.003},
		    {"T2.3", 				  101, 		 0.005}, 
		    {"T2.4", 				 1000,    	 0.005},
		    {"T2.5",				 1001,		 0.007},
		    {"T2.6", 		 9223372036854775807L, 		 0.007},
		    {"T2.7",		-9223372036854775807L, 		     0}, 
		    {"T2.8", 	   			    0,    	     0},
	};

	@DataProvider(name = "data")
	public Object[][] getTestData() {
		return testData;
	}

	@Test(dataProvider = "data")
	public void test(String id, long variable1,  double expected) {
		 assertEquals(InterestCalculator.interestRate(variable1), expected);
	}
}

7. Examination of test results

Console log

RemoteTestNG] detected TestNG version 7.4.0
PASSED: test("T2.6", 9223372036854775807, 0.007)
PASSED: test("T2.2", 100, 0.003)
PASSED: test("T2.4", 1000, 0.005)
PASSED: test("T2.5", 1001, 0.007)
PASSED: test("T2.7", -9223372036854775807, 0)
PASSED: test("T2.8", 0, 0)
PASSED: test("T2.1", 1, 0.003)
PASSED: test("T2.3", 101, 0.005)

===============================================
    Default test
    Tests run: 1, Failures: 0, Skips: 0
===============================================


===============================================
Default suite
Total tests run: 8, Passes: 8, Failures: 0, Skips: 0
===============================================

A MORE DETAILED LOOK AT BVA

• By definition, BVA covers all EP test coverage items
• With twice as many tests, the min and max of each EP has been tested at least once, using a min number of tests
• BVA focuses on finding errors with decisions
  • Decisions often fail at boundaries
  • E.g.x<0insteadofx<=0
• BVA often uncovers more errors than EP alone
• But has twice as many test cases --- a trade-off
• Boundary Values DO NOT OVERLAP
  • One value at top, one at bottom
• Goal: Achieve 100% coverage of boundary values

STRENGTHS AND WEAKNESSES OF EP

Strengths:

• Test data values are provided by the technique;
• Tests focus on areas where faults are more likely to be created by the developer.

Weaknesses:

• Doubles number of TCIs compared to EP;
• No Combinations.

KEY POINTS

• BVA is used to ensure correct processing with data values at start and end of every EP;
• Each BVA value is a test coverage item;
• Each BVA value is used as test case.

My thoughts

BVA is an important supplement to EP, this area is easy to be underestimated.