Test Case Generation | Set 1 (Random Numbers, Arrays and Matrices)

The test cases are an extremely important part of any "Software/Project Testing Process". Hence this Set will be very important for all aspiring software developers. The following are the programs to generate test cases.
 

• Generating Random Numbers 
   

• Generating Random Arrays
   

• Generating Random Matrix 
   

1. rand() Function- 
   -> Generate random numbers from the range 0 to RAND_MAX (32767) 
   -> Defined in <stdlib.h>/<cstdlib> header 
   -> If we want to assign a random number in the range - m to n [n >= m] to a variable var, then use-
   var = m + ( rand() % ( n - m + 1 ) ); 
   -> This function is a run-time function. So the values - n, m must be declared before compiling just like we have to declare the size of array before compiling. 
   -> Call this function every time you want to generate a random number
2. time() Function 
   -> Return the number of seconds from [00:00:00 UTC, January 1, 1970] 
   -> Defined in <time.h> header
3. srand(seed) 
   -> Generates random number according to the seed passed to it. 
   -> If this function is not used and we use rand() function then every time we run the program the same random numbers gets generated. 
   -> To overcome the above limitation, we pass time(NULL) as a seed. Hence srand(time(NULL)) is used to generate random values every time the program is made to run. 
   -> Always use this at the beginning of the program, i.e- just after int main() { 
   -> No need to call this function every time you generate a random number 
   -> Defined in <stdlib.h>/<cstdlib> header
4. freopen("output.txt", "w", stdout) 
   -> Writes (that's why we passed "w" as the second argument) all the data to output.txt file (The file must be in the same file as the program is in). 
   -> Used to redirect stdout to a file. 
   -> If the output.txt file is not created before then it gets created in the same file as the program is in.
5. fclose(stdout) 
   -> Closes the standard output stream file to avoid leaks. 
   -> Always use this at the end of the program, i.e- just before return(0) in the int main() function.