Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 12 | Testing
12.5 How would you test a pen?
SOLUTION
pg 70
This problem is largely about understand the constraints: what exactly is the pen? You
should ask a lot of questions to understand what exactly you are trying to test. To illustrate
the technique in this problem, let us guide you through a mock-conversation.
Interviewer: How would you test a pen?
Candidate: Let me find out a bit about the pen. Who is going to use the pen?
Interviewer: Probably children.
Candidate: Ok, that’s interesting. What will they be doing with it? Will they be writing, drawing,
or doing something else with it?
Interviewer: Drawing.
Candidate: Ok, great. On what? Paper? Clothing? Walls?
Interviewer: On clothing.
Candidate: Great. What kind of tip does the pen have? Felt? Ball point? Is it intended to
wash off, or is it intended to be permanent?
Interviewer: It’s intended to wash off.
…. many questions later ...
Candidate: Ok, so as I understand it, we have a pen that is being targeted at 5—10 year olds.
The pen has a felt tip and comes in red, green, blue and black. It’s intended to wash off clothing.
Is that correct?
…
The candidate now has a problem that is significantly different from what it initially seemed
to be. Thus, the candidate might now want to test:
1. Does the pen wash off with warm water, cold water, and luke warm water?
2. Does the pen wash off after staying on the clothing for several weeks? What happens if
you wash the clothing while the pen is still wet?
3. Is the pen safe (e.g.—non-toxic) for children?
and so on...
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Cracking the Coding Interview | Concepts and Algorithms