util method for programmatically run and verify TestNG test classes

TestNGUtils.java

public class TestNGUtils {

    private static final String LINE_SEPARATOR = System.getProperty("line.separator");

    public static void runAndVerify(Class<?>... testClasses) {

        if (ObjectUtils.isEmpty(testClasses)) {
            throw new AssertionError("no test class specified.");
        }

        // run testng tests
        TestListenerAdapter tla = new TestListenerAdapter();
        TestNG testNG = new TestNG();
        testNG.setTestClasses(testClasses);
        testNG.addListener(tla);
        testNG.run();

        List<ITestResult> failedTests = Lists.newArrayList();
        failedTests.addAll(tla.getFailedTests());
        failedTests.addAll(tla.getConfigurationFailures());
        if (!failedTests.isEmpty()) {
            String header = String.format("Combined Messages (Total:%d)", failedTests.size());

            List<String> errorMessages = Lists.newArrayList();
            errorMessages.add(header);
            errorMessages.addAll(Lists.transform(failedTests, new Function<ITestResult, String>() {
                int i = 1;
                @Override
                public String apply(ITestResult testResult) {
                    String stackTraceString = Throwables.getStackTraceAsString(testResult.getThrowable());
                    String template = "Message-%d: %n %s";
                    return String.format(template, i++, stackTraceString);
                }
            }));

            // transform messages to a single combined string
            String message = Joiner.on(LINE_SEPARATOR).join(errorMessages);
            throw new AssertionError(message);
        }
    }
}