"Some birds aren't meant to be caged, their feathers are just too bright"- Morgan Freeman, Shawshank Redemption. This blog is from one such bird who couldn't be caged by organizations who mandate scripted software testing. Pradeep Soundararajan welcomes you to this blog and wishes you a good time here and even otherwise.

Sunday, October 15, 2006

Answering the telephone puzzle

Hi Reader,

If you do not know what puzzle I put up in my previous post - read it now and then come back here to know how exciting the following information is.

Thanks for coming back and also welcome to those who have made an attempt to crack the puzzle.

_Answering the telephone puzzle_

I first want to announce the winner of the puzzle :
Sameer Chaudary . Congradulations Sameer!!

Many congrads to all others who made an attempt and sent me a mail. Some where close but most of them were wrong. I am impressed that quite a few freshers too made a great attempt to crack the puzzle.

Also the winner of the "best documentation recieved" is :
Suresh Marappa . Congradulations Suresh !

How could Sameer solve it?

This puzzle was simple to him as he had done the same mistake as people in my company did but still he does deserve the prize since he exhibited one quality of a good tester of being able to recollect the past learning.

If an excellent tester had solved it, it would be this way...

1. Ask me "What is your extension number?"

2. Ask me questions to try distinguishing whether humans or machines are causing this.

3. Ask me "What is my landline number and bangalore telephone exchange codes?"

4. Ask me "Whether is it really a missed call or are you not there when they call?"

5. Ask me "What time do you get the maximum number of calls or what is your working time?"

5. Ask me"Did you call back and ask one of them; how they reached my extension?"

Well that solved the puzzle, if I answer the above questions.

6. Further "List out all other possbilities"

Now, you would be interested to know who is that excellent tester who did crack the puzzle with his excellent approach. It is none other than my Guru James Bach, one of the leading Test Expert, we have been blessed with.

The only question he missed is to ask about mobile numbers from various service providers in Bangalore as he was running out of time and I had forcibly pulled him to solve this puzzle. However it is an easy task for someone who asked landline number to ask further about mobile numbers. I owe all my success to this great man who has helped me equip myself with skills to approach a problem in a right way through his masterpiece exercises.

How I identified the problem/solved the puzzle : ( I ask myself, a lot of questions. Thanks to James again )

1. "Pradeep is this a technical problem?"
Could be but let me think of other possibilities before I collect some evidence to say it is a technical problem

2. Is it that I am getting a missed call from the same number?
No, different people call at different times and this happens only during office hours and I hardly see a missed call in non office hours. Wow! this looks like its a human error!

3. Now that I got a clue that it could be a human error, what is causing all those people doing the same error?
Hmm! interesting. What is my extension number: 9986. When do people dial 9986?

Hey, wait a minute... Hutch Telecom operating in bangalore has a mobile number series of 99860 xxxxx , 99861 xxxxx , 99862 xxxxx , 99863 xxxxx , 9986x xxxxx

Ah ! I got it, people who who are trying to call a hutch number from their deskphone and missing a ZERO to be dialled as a prefix to make an external call are the ones who give me a missed call.

How do I confirm it? I could be wrong, I need some evidence, I am a tester.

While thinking I got another missed call. I immediately called the person who had given a missed call and asked ...
"Mam, I got a missed call from your number.. "

"Sorry, I tried calling some other number"... "Well may I know whether it is a hutch mobile you were trying to call?" ...
"Yes, how did you know that"...
"Just a guess, thanks for the info and have a nice day"

Bingo! This gives an evidence that it is not a technical problem and it is a human error.

Now why did I put this up as a puzzle to you all?

When you look at the problem as a tester as most of you did, you doubt the technology and conclude that it could be a bug but finally you see a human error causing the problem. This should give you a clue to think of human error also when someone asks you to analyze a bug.

Also, if you notice how I approached you would discover that although I was sure that 9986 and hutch numbers coincidence that created a problem, I did not want to conclude unless I get an evidence. Now that I have an evidence no one can deny my conclusion and that is a success for a tester when developers/managers dont deny a bug.

Also, I am happy that I could think of various other possibilities that I have not listed out here and I am sure whatever the problem had been, I would have found it out in a short while. More than a million thanks to my guru James Bach and his mind blowing exercises. I would say "that is the power of exploratory and rapid testing".

Now that does not mean I can solve any problem but that means I can get close to the solution at a faster pace and I can judge myself whenever I am wrong and learning to correct myself .

A special thanks to Sameer Chaudary who is the first person to make a contribution towards Tester Tested! since it is going to take new Avatar from next month.

Also, I am planning for a one day workshop in Bangalore next month (Nov-06) on "Acquiring testing skills through exercises" - Open to all testers. Keep watching for information or get in touch with me if you would want to join - pradeep.srajan@gmail.com. Of course it is not free and yet is affordable right from a fresher to an experienced person.

I just can't imagine how excited you would be when going back from the workshop. I have been testing my exercises on a few people already and it seems to be giving great results to people who are taking up those exercises.

I am not going to talk about "what is testing and what are the types and techniques" and if you are my regular reader you should have known by now that Tester Tested! is always different and not the usual stuff you find at a place/site near you.

If you intend to make this happen in your place, I am ready for it provided you pool up with other testers there and organize it. Do let me know your interests and other possibilities through mail - pradeep.srajan@gmail.com

"One small step towards becoming a good tester is your service to the community"
Thanks and Regards,
Pradeep Soundararajan


Mukesh said...

Hi Pradeep !
This was again a marvelous attempt by you. You always creates a enthusiasm to learn testing deeper and deepter. Thanks again for creating interest to learn a lot more for novice (like me) and it is useful to experienced as they get more to think.

victor said...


I am just mad at myself for just taking the puzzle as it was - without asking aditional questions.

I know questions are VERY good, but this time I tried to "guess" the solution.

Still, in my day-to-day work I ask the questions.

So, all, don't try to solve problems - first ASK QUESTIONS :).

Good luck,

Pradeep Soundararajan said...

Hi Victor and Mukesh,

Thanks and sure you can expect more. Tester Tested will keep testing brains... at least mine.

Michael said...

Dang--I solved this puzzle perfectly just now without seeing the answer, and Blogger screwed up my submission. However, it's fairly typical for James to solve a problem before I do. :)

---Michael B.

Pradeep Soundararajan said...


It is a pleasure to see you here again.

I would have loved to look through your approach and Blogger screwed up that too :(

IMO it is typical for James to solve a problem before most of us do :)

Anonymous said...

Good Puzzle. Even I thought of solving it without asking any questions. I am a developer.
Moral of this is too Good...
Don't try to solve problems - first ask all related questions about the Problem :).

seju said...

Great puzzle! How come it didn't strike me!?! :( Coz the reception's desk extension at my office is 9 and when I'd just joined the company I used to commit this mistake of directly dialling the external numbers without initially pressing the activation code i.e '07' and you all know every Indian mobile card number starts with a '9'and I'm wondering how many more in the office were like me loading the poor receptionist with millions of missed calls everyday! Lol

57.5 Just Pass said...

Dear pradip/others ,

just have doubt in these conversation , if those people by mistake call without pressing the number '0' [in pradip's case] how could it end up a missed call , it would be only a wrong call , isnt ? kindly clarify ..

Pradeep Soundararajan said...

@ 57.5,

How many times have you disconnected the call realizing you were calling the wrong number?

The same could have happened. Wrong call from the caller perspective and missed call from the receiver perspective.

kothwal2007 said...

Hi Pradeep,
Its interesting to know the puzzle's answer.. but actually thats good to know a approach to solve a problem.. but i actly i have one small doubt even the puzzle , ur thoughts sounds good and understandable.. n here my question is .. "to my knowledge the Extension number will be dialed in the last.. as u said ur extension is 9986. then it should be suffixed to ur number. i.e say ur number is 123456 then if u happen to get a call.. then the number to reach u should be 1234569986..?? plz tell me if i'm wrong??"

Preethi Anish said...

i was clueless ( :( )
please do upload more thought provoking articles like this ...