Index: src/main/java/org/codehaus/mojo/cobertura/CoberturaInstrumentMojo.java
===================================================================
--- src/main/java/org/codehaus/mojo/cobertura/CoberturaInstrumentMojo.java	(revision 4684)
+++ src/main/java/org/codehaus/mojo/cobertura/CoberturaInstrumentMojo.java	(working copy)
@@ -22,6 +22,7 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
@@ -30,11 +31,13 @@
 import org.apache.maven.artifact.ArtifactUtils;
 import org.apache.maven.artifact.factory.ArtifactFactory;
 import org.apache.maven.artifact.handler.ArtifactHandler;
+import org.apache.maven.model.Plugin;
 import org.apache.maven.plugin.MojoExecutionException;
 import org.codehaus.mojo.cobertura.configuration.ConfigInstrumentation;
 import org.codehaus.mojo.cobertura.tasks.InstrumentTask;
 import org.codehaus.plexus.util.FileUtils;
 import org.codehaus.plexus.util.IOUtil;
+import org.codehaus.plexus.util.xml.Xpp3Dom;
 
 /**
  * Instrument the compiled classes.
@@ -146,12 +149,63 @@
             {
                 IOUtil.close( fos );
             }
+            
+            // Even better way, no need for a patched Cobertura.
+            if ( project.getBuildPlugins() != null ) {
+            	for ( Iterator iterator = project.getBuildPlugins().iterator(); iterator.hasNext(); ) {
+	        		Plugin plugin = (Plugin) iterator.next();
+	        		if ("org.apache.maven.plugins".equals( plugin.getGroupId() ) && 
+	        				"maven-surefire-plugin".equals( plugin.getArtifactId() ) ) {
+	        			addDatafileConfiguration((Xpp3Dom)plugin.getConfiguration());
+	        		}
+            	}
+            }
 
             // Set the instrumented classes to be the new output directory (for other plugins to pick up)
             project.getBuild().setOutputDirectory( instrumentedDirectory.getPath() );
             System.setProperty( "project.build.outputDirectory", instrumentedDirectory.getPath() );
         }
     }
+    
+    /**
+     * Adds Cobertura runtime configuration to the Maven Surefire plugin
+     * configuration, so that the instrumented unit tests can find the
+     * Cobertura datafile.
+     * <p>
+     * This is the equivalent of having the following configuration in
+     * the project's pom:
+     *      &lt;plugin&gt;
+     *          &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
+     *          &lt;artifactId&gt;maven-surefire-plugin&lt;/artifactId&gt;
+     *          &lt;configuration&gt;
+     *              ...(existing configuration)...
+     *              &lt;systemProperties&gt;
+     *                  &lt;property&gt;
+     *                      &lt;name&gt;net.sourceforge.cobertura.datafile&lt;/name&gt;
+     *                      &lt;value&gt;${project.build.directory}/cobertura/cobertura.ser&lt;/value&gt;
+     *                  &lt;/property&gt;
+     *              &lt;/systemProperties&gt;
+     *          &lt;/configuration&gt;
+     *      &lt;/plugin&gt;
+     * 
+     * @param configuration The Maven Surefire plugin configuration node.
+     */
+    private void addDatafileConfiguration(Xpp3Dom configuration) {
+		// set the cobertura datafile property to be passed to the unit tests.
+		Xpp3Dom props = configuration.getChild("systemProperties");
+		if (props == null) {
+			props = new Xpp3Dom("systemProperties");
+			configuration.addChild(props);
+		}
+		Xpp3Dom property = new Xpp3Dom("property"); 
+		props.addChild(property);
+		Xpp3Dom name = new Xpp3Dom("name");
+		name.setValue("net.sourceforge.cobertura.datafile");
+		property.addChild(name);
+		Xpp3Dom value = new Xpp3Dom("value");
+		value.setValue(dataFile.getPath());
+		property.addChild(value);
+    }
 
     private void addCoberturaDependenciesToTestClasspath()
         throws MojoExecutionException
Index: src/test/java/org/codehaus/mojo/cobertura/stubs/InstrumentMavenProjectStub.java
===================================================================
--- src/test/java/org/codehaus/mojo/cobertura/stubs/InstrumentMavenProjectStub.java	(revision 4684)
+++ src/test/java/org/codehaus/mojo/cobertura/stubs/InstrumentMavenProjectStub.java	(working copy)
@@ -25,6 +25,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Set;
@@ -68,7 +69,11 @@
         return build;
     }
 
-    public Artifact getArtifact()
+	public List getBuildPlugins() {
+		return new ArrayList();
+	}
+
+	public Artifact getArtifact()
     {
         return new ArtifactStub();
     }