void runTestSuite( String testClassName ) {
Test suite = getTest( testClassName );
if (suite != null) {
TestResult testResult = new TestResult();
testResult.addListener( this );
long startTime= System.currentTimeMillis();
suite.run( testResult );
long endTime= System.currentTimeMillis();
_formatter.displayResults( _writer, testClassName, elapsedTimeAsString( endTime-startTime ), testResult );
}