OnceOnlySuite.java

package org.eclipse.cdt.tests.dsf.gdb.framework;

import java.util.HashSet;
import java.util.Set;

import org.junit.internal.builders.IgnoredClassRunner;
import org.junit.runner.Runner;
import org.junit.runners.Suite;
import org.junit.runners.model.InitializationError;
import org.junit.runners.model.RunnerBuilder;

	
/**
 * This custom suite runner ensures that a class runs only once, no matter how
 * many times it appears in a suite. Redundant appearances are possible with
 * hierarchical suites. In some cases, this is intentional and desirable--i.e.,
 * we want the same class to run multiple times (usually with some slight
 * variation). However, in some cases, the redundant appearances are
 * unintentional and unavoidable consequences of how the suites are defined and
 * used. This runner caters to the latter scenario.
 * 
 * <p>
 * Thanks to Bill Venners and David Saff for suggesting this solution on the
 * junit mailing list. See <a
 * href="http://tech.groups.yahoo.com/group/junit/message/23208"
 * >http://tech.groups.yahoo.com/group/junit/message/23208</a>
 */
@SuppressWarnings("restriction")
public class OnceOnlySuite extends Suite {
   private static Set<Class<?>> alreadySeen = new HashSet<Class<?>>();
   
   public OnceOnlySuite(Class<?> testClass, final RunnerBuilder builder) throws InitializationError {
       super(testClass, new RunnerBuilder() {
    	   @Override
			public Runner runnerForClass(Class<?> testClass) throws Throwable {
	               if (alreadySeen.contains(testClass)) {
	                   return new IgnoredClassRunner(testClass);
	               }
	               alreadySeen.add(testClass);
	               return builder.runnerForClass(testClass);
	           }
	       });
   }
}