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I played around a bit with iteration using JUnit today. I have some generic tests that behave differently depending on the values fed to them. I don’t want to have iteration code living alongside each test (maintenance nightmare), so I wanted to use JUnit’s @Parameters tag to pull in my test data via a Preferences file and do the iteration for me.

It took me longer than I expected to get right, mostly because static methods annoy me and trip me up a bit. (Your parameters method must be static in order for it to work).

However, get it working I did. On the off chance that it saves someone else some time, here’s how it works:

import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Properties;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class paramTest
{
	final static String dataFile = "/dataDriver.txt";
	private String words;

	public paramTest(String words)
	{
		this.words = words;
	}

	@Test
	public void verifyThing() throws Exception
	{
		System.out.println("key: " + words);
	}

	@Parameters
	public static Collection data()
	{
		Collection returnList = new ArrayList();
		InputStream dataStream = paramTest.class.getResourceAsStream(paramTest.dataFile);
		Properties dataProperties = new Properties();
		try{
			dataProperties.load(dataStream);
		} catch(Exception e)
		{ System.out.println(e);}

		Enumeration e = dataProperties.propertyNames();
		while (e.hasMoreElements())
		{
			returnList.add(new Object[]{dataProperties.getProperty((String) e.nextElement())});
		}
		return returnList;
	}
}

Interestingly enough, the data comes back in the reverse order that it exists in the preferences file. Something to keep in mind if you want your tests to run in a certain order.