BlackJack.java

package main;

public class BlackJack {

	public int play(int a, int b) {
		if (a > 21 && b > 21) {
			return -1;
		} else if (a > 21) {
			return b;
		} else if (b > 21) {
			return a;
		} else {
			return Math.max(a, b);
		}

	}

}

BlacklJackTest.java

package testing;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

import main.BlackJack;

public class BlacklJackTest {

	BlackJack blckJck = new BlackJack();

	@Test
	public void testP1Wins() {
		assertEquals(20, this.blckJck.play(20, 16));
	}

	@Test
	public void testP2Wins() {
		assertEquals(20, this.blckJck.play(16, 20));
	}

	@Test
	public void testOneBust() {
		assertEquals(2, this.blckJck.play(2, 24));
	}

	@Test
	public void testBothBust() {
		assertEquals(-1, this.blckJck.play(25, 36));
	}

}