Random element in an array

    In performance testing, we sometimes need to deal with a list of values.  For example, when we test an e-commerce web site, we may need to extract a list of products from a page.  With the list/array extracted, we can do operations such as randomly picking an item to view or to add to cart.  On some platform, this logically simple operation can be a daunting job.

    Saw an interesting blog by Howard Clark on testing Peoplesoft Financials 9.0 using loadrunner: "Randomly Selecting an Array of Values and Using That Value As A Parameter".  Here is the script to pick a random BUID copied from that blog. It's listed here just to show how complex it is - you don't have to read it.

 int TotalNumberOfBUIDs;  
 char TotalNumberOfBUIDschar[3]; //working variable  
 char *AvailableBUIDsparam; //working variable  
 web_reg_save_param(“AvailableBUIDs”,  
 “LB/IC=class=’PSSRCHRESULTSODDROW’ >”,  
 “RB/IC=”,  
 “Ord=All”,  
 “Search=Body”,  
 “RelFrameId=1″,  
 “Notfound=error”,  
 LAST);  
 TotalNumberOfBUIDs=atoi(lr_eval_string(“{AvailableBUIDs_count}”));  
 TotalNumberOfBUIDs = rand() %TotalNumberOfBUIDs;  
 lr_output_message(“%d”, TotalNumberOfBUIDs);  
 itoa(TotalNumberOfBUIDs, TotalNumberOfBUIDschar, 10); //working variable conversion  
 lr_save_string(TotalNumberOfBUIDschar, “BUIDindex”);  
 AvailableBUIDsparam = lr_eval_string(“{AvailableBUIDs_{BUIDindex}}”);  
 lr_save_string(AvailableBUIDsparam, “BUIDs”);  
 lr_save_string((lr_eval_string(lr_eval_string(“{BUIDs}”))), “BUID”);  
 “Name=VCHR_ERRC_WRK_BUSINESS_UNIT”, “Value={BUID}”, ENDITEM, //application of the value that was captured and then randomized  

    While I was impressed by the author's skills in C,  I couldn't help wondering how an average test engineer can do this.  They know their test subject well, but writing such complex C program can be well above their heads.   On Netgend platform, it's so much easier.

 AvailableBUIDs = substring(str, "class=’PSSRCHRESULTSODDROW’ >", "<", "all");  
 TotalNumberOfBUIDs = length(AvailableBUIDs);
 BUIDindex = randNumber(0, TotalNumberOfBUIDs-1); //indexing is 0 based  
 BUID = AvailableBUIDs[BUIDindex];  //variable "BUID" now contains a random value.

    Even though we tried to use the same variable names as in loadrunner script, our script is still much shorter and easier to understand.  Here are some of the reasons for the simplicity:

• In a NetGend script, all variables are local to an instance/Vuser.  There is no need to use API to get the value of a variable (called "parameter" in Loadrunner) into code space or write the value back to the variable after some operations in the code space.
• NetGend supports the array variable.  In this case, the variable "AvailableBUIDs" holds the array of extracted BUIDs.
• You can get the length of the array by the function "length()".
• You can get any element in the array by indexing using [].  For example: AvailableBUIDs[BUIDindex] gives the value of "BUIDindex+1"th element. (it's 0 based)

    Note that the above short script (4 lines) can be made even shorter.   The readability may suffer a little bit but it's still fairly easy to understand. 

 AvailableBUIDs = substring(str, "class=’PSSRCHRESULTSODDROW’ >", "<", "all");  
 BUID = AvailableBUIDs[randNumber(0,length(AvailableBUIDs)-1)];  

    A good performance test platform needs to make complex test scenarios simple, not the other way around.