Installing and using Code Coverage plugin in NetBeans 6.5

One of techniques to ensure that software is properly and thoroughly tested is to get code coverage information and find which blocks of code weren’t executed at all.

There is a number of code coverage tools for Java applications. One of them, free and mature is Emma ( http://emma.sourceforge.net/ ) which is one used by NetBeans code coverage plugin.

Installing plugin

To install plugin, select Tools -> Plugins and choose “Code Coverage” in the list of available plugins:

After accepting license terms, plugin is ready for use.

Activate Code Coverage plugin in a project

To activate plugin, right click on project name in Projects view and click on Coverage -> Activate Coverage Collection.

Using Code Coverage Plugin

I’ll try to demonstrate usage of Code Coverage plugin with one simple example. Create a new project and add following class to it:

package coverage;
public class Main {

    public void testMethod() {
        verify(1);
    }

    private String check(String a) {
        return "";
    }

    private String verify(int i) {
        StringBuffer retVal = new StringBuffer("verified.");
        if(i == 0) {
            retVal.append("i == 0");
        }
        if(i == 1) {
            retVal.append("i == 1");
            if(i == 2) { /* partial coverage */ retVal.append("i == 2");}
        }
        return retVal.toString();
    }
}

To test it, in test packages create following class, in the same package (coverage):

package coverage;

import junit.framework.TestCase;

public class MainTest extends TestCase {

    public MainTest(String testName) {
        super(testName);
    }

    public void testOne() {
        Main m = new Main();
        m.testMethod();
    }
}

To see plugin in action, activate Code Coverage for a project as described above and run Test from context menu. When the execution finishes (it will be fast), we can check the results.

Seeing coverage results for a class

To see coverage results for one class, double click on it in Projects View. In the example below there are lines in two colors:

• green lines were covered completely
• yellow lines are executed partially – in example below, condition “if (i == 2)” was executed, but rest of the line was not

Coverage results for one class

Project Coverage Report

Code Coverage plugin also provides report for entire project. To see it, right click on the project name and choose Coverage -> Show Project Coverage Statistics:

Project report looks like this:

Project Code Coverage Report

In the report we can check package coverage for classes and lines of code and class coverage for individual classes.

Useful Links

Code Coverage [Wikipedia.org]

NetBeans Unit Tests Code Coverage plugin [NetBeans.org]

Getting Help

If you have problems with installing or running Code Coverage plugin, describe your problem in a comment and I’ll try to help. I can answer in English, French and Spanish.