- I have to install Mosh on both the server and the client. I installed Mosh on both my the OS X and my Ubuntu 64-bit server.
- OS X's terminal is, by default, sending its LC_* environment variable when you SSH to another machine. LC_CTYPE is set to UTF-8 by default and it is fine under OS X Lion. But when this is send to my Ubuntu server, it caused a problem with setlocale call. Must comment out SendEnv line in /etc/ssh_config on my Mac. Thanks to tip from this page! - http://thegreyblog.blogspot.com/2012/02/fixing-mac-os-x-lions-ssh-utf-8-issues.html
Tuesday, April 10, 2012
Sunday, September 25, 2011
Interesting post. I'm in my first years practicing unit testing too. Won't miss leaving a long comment here!It seems the very problem about unit testing for you is about maintainability of the test cases. It was a question for me too about how many tests to write for particular class. The lower number of tests you write, the lower maintainance problems, right?There are some occassions I avoid writing tests for. I am not claiming these are right or wrong but it seems to work for me.#1: During our undergrad years, I was introduced to unit testing (with JUnit.) What I remembered are that we are encouraged to write tests for as many methods as possible. We even generated the tests for plain getter/setters. Come to think of it now, that was totally unpractical!So now I just skip the simple methods I am sure there are only silly test cases for it.#2: Another thing is about writing test for private methods. When you design a class, you are giving your users some kind of contract by providng public methods. These are something that should be broken or be changed often. If you need to change these often, you may have to admit the class is incorrectly designed and thus rewrite/add the tests.However, I do not test private methods. This give me some room of flexiblity where I can change/optimize/organize the inner working of the class. I can change the signature/working of private methods any way I would like to, but I just need to make sure the public methods do pass the tests.#3: I do have some tests you referred to as 'small acceptance tests.' However, to perform 'unit' testing, you test one and only one class. If the class depends on some other concrete classes then you have to change them to abstract/interface instead. If you are testing more than one classes than that may be considered as 'integration' testing, or some other names.That was quite hard core! While I know this, I don't mock out some dependencies for small classes. That would require some efforts. But still, I would write integration tests for it.Clearly, innovations in our world do not start with requirements from users. So all these models starting from requirement gathering are all WRONG. If you want to introduce something now, use whatever you like and do whatever you want to. But if you are building something big, you must also need to look into the rear mirrors and you do need some confidence going forward. Unit tests, test coverage, etc. are some of the answers to that.
Sunday, July 10, 2011
I got hit by an interesting problem of “Zebra Puzzle” the other day. It is a well known logic puzzle believed to be first invented by Albert Einstein.
The question here is, how do we use our favorite programming language to solve this problem?
Wikipedia suggests the following algorithm for generating all permutation systematically.
The following algorithm generates the next permutation lexicographically after a given permutation. It changes the given permutation in-place.
- Find the largest index k such that a[k] < a[k + 1]. If no such index exists, the permutation is the last permutation.
- Find the largest index l such that a[k] < a[l]. Since k + 1 is such an index, l is well defined and satisfies k < l.
- Swap a[k] with a[l].
- Reverse the sequence from a[k + 1] up to and including the final element a[n].
I have put the working example on http://www.solidskill.net/ZebraPuzzle.htm. There are other parts of code that search through the solution space, setup the constraints for Zebra puzzle. But they are not discussed here.
There are some things to note about this implementation though. First, it is not very efficient. You can see in the getNextSequence(..) loop that there are loops used to search for k and l that satisfy the conditions.
Hope this helps those who are looking for permutation generation code.