Comments on: Unit Testing “Where’s The Dollar?”

By: Erik

Erik — Wed, 06 May 2009 16:35:55 +0000

I think the point of the exercise was that you should always be careful when turning business requirements into code, no matter what method you use.

By: Chris Missal

Chris Missal — Wed, 06 May 2009 15:49:16 +0000

@Matthew

You are correct, this is a poorly designed test, but note that it is tagged under “For Fun” ;)

By: Matthew

Matthew — Wed, 06 May 2009 15:36:51 +0000

The tests are also improper in their usage of certain numbers. The tests are written to prove or disprove equality conditions among variable expressions… testing if they equal 30, or 29 or 105 is poor design, and encourages the practical inadequacies of the test.

By: Chris Missal

Chris Missal — Wed, 06 May 2009 15:08:52 +0000

@David

You’re correct in the flaw in the riddle. It is asking you to add money spent with money earned. Like saying that if I gave you $1 and you earned $1 from it, we have $2. Which is just bad logic.

@Joshka

You’re also correct that the test is incorrect; the test falls under the same mistakes that the riddle enforces, the credit/debit actions cannot be added together like they are. The Front desk should start at $0 if the guys start at $10. This requires a rework of the tested logic, thus causing the test to fail.

By: Joshka

Joshka — Wed, 06 May 2009 14:50:06 +0000

The last line should read:
Assert.That(GuyOne + GuyTwo + GuyThree – BellBoy, Is.EqualTo(FrontDesk));

The code is flawed in that GuyOne,Two,Three represent credits but bellboy and frontdesk represent debits (or the vice versa, I forget which).
Either way, your intransient condition is that no money is created in the system, i.e. bell + guys + frontdesk = 30

By: David Morton

David Morton — Wed, 06 May 2009 14:44:14 +0000

It’s in the riddle.

The men paid 27 dollars total, 25 of which went to the hotel, and 2 of which went to the bellboy. The error is in adding the amount of money the men spent to the amount of money the bellhop _received_. The amount of money received should be subtracted from the amount of money spent, and the values are equal.