PathTranslator translator = new DefaultPathTranslator();
ModelInterpolator interpolator = createInterpolator( translator );
File basedir = new File( System.getProperty( "java.io.tmpdir" ), "base" );
String value = interpolator.interpolate( "${project.build.outputDirectory}/foo", model, basedir, new DefaultProjectBuilderConfiguration(), true );
value = value.replace( '/', File.separatorChar ).replace( '\\', File.separatorChar );
String check = new File( basedir, "target/classes/foo" ).getAbsolutePath();
check = check.replace( '/', File.separatorChar ).replace( '\\', File.separatorChar );