20.2 Junit Parameterized Test

import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;

import java.util.Arrays;
import java.util.Collection;
import java.util.Random;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

 @RunWith(Parameterized.class)
public class NumbertoWordsConverterTest {

private int input;
private String expected;
private Random random = new Random();

    @Parameters
    public static Collection<Object[]> parameters() {

        // TODO 1: As your code passes each test uncomment the next parameter
        // pair. Don't
        // forget to throw an IllegalArgumentException if the number is out of
        // the
        // prescribed range. You will probably go through several strategies
        // before you
        // settle for one.

        Object[][] data = new Object[][] { { 1, "one" }, { 0, "zero" },
                { 7, "seven" }, { 11, "eleven" }, { 12, "twelve" },
                { -2, "minus two" }, { 17, "seventeen" }, { 20, "twenty" } };
        return Arrays.asList(data);
    }

    public NumbertoWordsConverterTest(int input, String expected) {
        this.input = input;
        this.expected = expected;
    }

    @Test
    public void testConvert() {
        assertThat(new NumbertoWordsConverter().convert(input),
                is(equalTo(expected)));
    }

    @Test(expected = IllegalArgumentException.class)
    public void testOutOfRange() {
        // Cook up an int that is out of range.
        int testNumber = random.nextInt();
        while (Math.abs(testNumber) <= 20) {
            testNumber = random.nextInt();
        }
        new NumbertoWordsConverter().convert(testNumber);
    }
}