Boundary Value Test Cases, Robust Cases and Worst Case Test Cases

Generate boundary Value analysis, robust and worst-case test case for the program to find the median of three numbers. Its input is a triple of positive integers (say x, y, and z) and the minimum value can be 100 and maximum can be 500.

Median of three numbers is the middle number when all three numbers are sorted.

Example –

10, 40, 20

In this case, the median is 20 (10, 20, 40).

1. Boundary Value Test Cases are –

for x, y, z :
min value = 100
close to min = 101
nominal = 300
close to max = 499
max = 500 

Test cases are,

4*3 + 1 = 13 

X	Y	Z	Median
100	300	300	300
101	300	300	300
300	300	300	300
499	300	300	300
500	300	300	300
300	100	300	300
300	101	300	300
300	499	300	300
300	500	300	300
300	300	100	300
300	300	101	300
300	300	499	300
300	300	500	300

2. Robust Test Cases –
Here, we go outside the legitimate boundary, it is an extension of boundary value analysis.

for x, y, z :
min value : 100  
close to min : 101  
nominal : 300 
close to max : 499 
max : 500 
lesser than min value : 99 
larger than max value : 501  

Total test cases,

= 6*n+1 = 6*3+1 = 19 

So there will be extra 6 cases apart from the above 13 cases –

X	Y	Z
99	300	300
501	300	300
300	99	300
300	501	300
300	300	99
300	300	501

3. Worst Test Cases –
If we reject “single” fault assumption theory of reliability, and consider cases where more than 1 variable has extreme values, then it is known as worst case analysis.

Total no. of test cases,

5^n = 5^3 = 125 cases 

X	Y	Z	Median
100	100	100	100
101	100	100	100
300	100	100	100
499	100	100	100
500	100	100	100
100	101	100	100
101	101	100	101
300	101	100	101
499	101	100	101
…	…	…	…

Mathematically, the test cases will be a cross product of 3 sets –

  {100, 101, 300, 499, 500} 
x {100, 101, 300, 499, 500} 
x {100, 101, 300, 499, 500}

Let set A,

= {100, 101, 300, 499, 500}

So, the set of worst cases will be represented by,

= A x A x A