some reflection magic to help writing table based tests

TestHelper.java

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;

public final class TestHelper {

	public static void test(Object[][] tests, Object target, String methodName, Class<?>...argsTypes) throws Exception {
		Class<?> baseClass;
		if (target instanceof Class) {
			// static method
			baseClass = (Class<?>) target;
			target = null;
		} else {
			baseClass = target.getClass();
		}
		Method method = baseClass.getDeclaredMethod(methodName, argsTypes);
		if (!method.isAccessible()) {
			method.setAccessible(true);
		}
		// iterate over test data arrays (arguments for tested method followed by expected value)
		// and if the expected value is a real value check and compare the result.
		// If it's an Exception, catch it and compare class and message with expected Exception.
		// This does not account for methods returning Exceptions.
		try {
			Object[] args = new Object[method.getGenericParameterTypes().length];
			for (int i = 0; i < tests.length; i++) {
				Object[] test = tests[i];
				final String message = "case " + i + ": " + Arrays.toString(test);
				// expected is always the last value
				final Object expected = test[test.length - 1];
				System.arraycopy(test, 0, args, 0, test.length - 1);
				try {
					final Object actual = method.invoke(null, args);
					if (actual == null || expected.getClass() != actual.getClass()) {
						throw new RuntimeException("actual and expected values do not match in " + message);
					}
					// compare with expected int, Date, String, ...
					assertEquals(message, expected, actual);
					continue;
				} catch (InvocationTargetException e) {
					if (e.getTargetException().getClass() == expected.getClass()) {
						// compare with expected Exception by class and message
						assertEquals(message,
								((Exception) expected).getMessage(),
								e.getTargetException().getMessage()
						);
						continue;
					}
					// detailed exception message mentioning failed test case
					throw new RuntimeException(message, e);
				}

			}
		} catch (IllegalAccessException e) {
			fail(e.getMessage());
		}
	}
}

And here is a helper method to mark unreachable code and get parameter information:

    // helper method for exceptions in unreachable locations
    private static RuntimeException unreachable(Throwable t, Object... args) {
        StringBuilder builder = new StringBuilder("PANIC for (");
        if (args.length > 0) {
            builder.append(args[0]);
            for (int i = 0; i < args.length; i++) {
                builder.append(", ").append(args[i]);
            }
        }
        builder.append("). Contact the maintainer");
        if (t != null) {
            return new RuntimeException(builder.toString(), t);
        }
        return new RuntimeException(builder.toString());
    }