My experience with unit testing in software development

I am not a fan of software engineering which is taught in school. Waterfall model, spiral model,  many blah blah phases ,diagrams and documents. I usually thought of those as useless works or not worth to do.  I thought that software development should be simple. Get requirement -> Draft design -> Go coding! ->  Debug -> Someone test it manually -> Debug -> Test again (until it's acceptable) -> OK, Finished

Documentation should exist only if it is essential and the source code is one of the documentation. This methodology works fine because I usually develop alone or in a small team and the software does not have many modules.

Unit testing is one of those which I thought it's not worth to do. I agree that's it's useful for regression test of the code but I thought I know what I've done with my code and know what are affected. 

Around two years ago, I and my colleagues started a new project. One of them wanted to try a kind of Agile development model (I don't know the name. I've said I'm not a fan of these models) and we tried.

He encouraged me to write the unit test for each class and a few acceptance tests for overall project behaviors. I did it because I wanted to give it a try too.

Then I know I was wrong about testing. I usually see some bugs because the tests fail. In addition, I feels great when all the tests go green. The tests guarantee that the software still work as it should. However, I see some disadvantages or difficulties in writing test.

VisualVM on ubuntu(lucid) failed to initialize the Profiler engine

I installed VisualVM on my lucid(amd64), luanch it and it shows an error.

Failed to initialize the Profiler engine: Problem with a required JFluid installation directory or file /usr/lib/jvm/java-6-openjdk/lib/visualvm/profiler3/lib/deployed/jdk16/linux-amd64/libprofilerinterface.so Original message: File does not exist.

In sprite of this error, the visualvm still can run but profiler/sampler doesn't show up.
Someone have filed this bug here. To fix this problem, recompile the missing lib manually and move to the right place.
Here are the steps

1. Download visualvm source here (visualvm_1.2.2.orig.tar.gz at the right pane)
2. Extract it and cd to the build directory
   tar -xzvf visualvm_1.2.2.orig.tar.gz
   tar -xzvf netbeans-profiler-visualvm_release68.tar.gz
   cd lib.profiler/native/build
3. You will see build script ( buildnative-linux64.sh ) then edit it. 
1. Replace gcc32 with gcc
2. Change 2 BuildJDK lines to below. /usr/bin/jvm/default-java/ is my jdk path; yours may differ.
   BuildForJDK "/usr/lib/jvm/default-java" "jdk16"
4. Make directory for release
   mkdir -p ../../release/lib/deployed/jdk16/linux-amd64/
5. Run this build script. It will compile the source against jni headers in our jdk and output as libprofilerinterface.so
   ./buildnative-linux64.sh
6. Move libprofilerinterface.so to the right place in your jdk path
   sudo cp ../../release/lib/deployed/jdk16/linux-amd64/libprofilerinterface.so /usr/lib/jvm/default-java/lib/visualvm/profiler3/lib/deployed/jdk16/linux-amd64/
7. Launch VisualVM again.