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andymock
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raven conway
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Justin Kemp
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kailis
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In fact I went through the TDD Kata for this problem on the train yesterday and the solution was actually slightly different, in fact I think better.

I did not add any exception handling as this was not a 'requirement' but I take your point that this should really be covered.

i /= << I was the same as you at first, but this is one I think really should be learnt. we do += and -= all the time so it's not that challenging.

And great to see you spotted a bug in my tests

Going to post a web cast of doing the process so that people understand the technique and reason for some of the refactorings.

Great post. The more we can do to persuade people using TDD or even just unit testing the better.

There's a few things I'd do differently to make it more readable IMHO. All really minor though.

1. I wouldn't use i as a parameter name for a method. It's confusing as it's normally limited to internal for loops an hence isn't descriptive.
2. I'd consider throwing an ArgumentOutOfRangeException if a negative number was passed in to clarify the use. People might expect it to return the primes as though it was a positive number. I certainly did until I looked up getting the prime factors of a negative number.
3. AddPrimeToProductsAndReduce. I found it easier to read moving the 2 lines back into the method it's called from. I'd agree on an extract method refactoring if there was more to AddPrime and Reduce, but as the method does 2 things in 2 lines of code it seems superfluous. IsDivisable on the other hand is clearer than the line of code it replaces.
4. Depending on who will also be looking at the code I'd write out i /= prime longhand to i = i / prime. /= isn't often used, in fact I don't think I've ever seen it outside documentation before. I had to stop and think what it was doing rather than just glance at the line and know. Could just be my problem of course!
5. The private methods don't use any instance variables so could/should be static. FxCop would tell you to do this.
6. And this one really is minor. The problem said that the method should be static.
7. There's a bug in your test Generate_NonPrimeNumberNotDivisableByTwoWithTwoProducts_ReturnProducts. It tests the first item in the output list twice.
8. Generate_PrimeNumber_ReturnPrimeNumber. I'd call the parameter something like prime so it's clear it's the input as well as the expected result.

Keep up the good work.
Richard

If in the example I want to find the Prime Products for 8 (which is 2,2,2) I cannot see how Yield would return this. I may be missing something, would be interested to see a code sample.

The other problem I suspect with Yield is that it is not that well used, doesn't mean it's wrong, but adding this to any code would mean most developers would be saying WTH – how does this work?

If in the example I want to find the Prime Products for 8 (which is 2,2,2) I cannot see how Yield would return this. I may be missing something, would be interested to see a code sample.

The other problem I suspect with Yield is that it is not that well used, doesn't mean it's wrong, but adding this to any code would mean most developers would be saying WTH – how does this work?