Unit testing? help.

Question

OK, I have tried to rap my mind around this for a few days. Unit testing.
I understand the whole:
if(expected)
System.out.println("OK");
else System.out.println("Error");Part of my class assignment but, I am still confused. Could someone explain how unit testing works? (*No, I don't want you to do it for me or anything like that.*) I am just confused on how exactly to test for these things in Java. I understand that I need to add some kind of input then check the return value with what is expected. However, I am not sure how to implement it.
Currently I tried something:
public static void lastIndexOfTest(MyString ms, int pos, char expected){
          System.out.println("Testing lastIndexOf("+pos+") on MyString " + ms);
          System.out.println("Expected: " + expected);
          try{
               int got = ms.charAt(pos);
               System.out.println("Got: " + got);
               if(got == expected)
                    System.out.println("OK");
               else
                    System.out.println("Error2");
          catch(Exception e) {
               System.out.println("Error: " + e);
          }That works in the sense that it give me no errors. But, because I don't understand how the code works exactly for everything I am not sure at all if it is even returning something thats correct.
Here is my assignment:
http://www.csl.mtu.edu/cs1122/www/programs/prog1/desc.html
Are there any tutorials on how to do unit testing? I have been looking all over and can't seem to find any listed on Google.

Answer 1

shawnw wrote:
OK, I have tried to rap my mind around this for a few days. Unit testing."Unit" == "one thing". You're testing each individual part of your program that can be considered a single functional unit (not necessarily a single class).
Although I've heard people say "unit testing" to apply to just about everything.
That works in the sense that it give me no errors. But, because I don't understand how the code works exactly for everything I am not sure at all if it is even returning something thats correct.Well, obviously, knowing what's correct is necessary before you can test for correctness.
Typically, you introduce specific test data to the thing being tested, and you know the correct response for that test data.
For example if you're testing a factorial program, you know that 3! == 6.
If you have a bit of (your own code) and you don't know what correct behavior of that code is, then you're not done. Really you shouldn't have started coding if you didn't know what you were trying to accomplish when you were done.
In test-driven development, you write the test before you write the code. Among other things, this ensures that you know what a bit of code is supposed to accomplish before you even start, which is a good thing.
Here is my assignment:
http://www.csl.mtu.edu/cs1122/www/programs/prog1/desc.html
Are there any tutorials on how to do unit testing? Didn't your professor mention it in class?
I have been looking all over and can't seem to find any listed on Google.I find that hard to believe. If I Google "unit testing tutorial" I find a bunch. But several of those are specific to particular environments, so maybe that's what's throwing you off.
The canonical unit testing framework for Java is JUnit. You might want to google for JUnit tutorials (I just did and found some).