JUnit実践入門を読んでいて，Theoryアノテーションを試してみたいと思ってたところ，ちょうどよさげな問題を解いたブログ「3年間の進歩 - uehaj's blog」( http://uehaj.hatenablog.com/entry/2013/01/09/125407 ) がポストされていたので，やってみた．

Cards.java

import java.util.Arrays;
 
public class Cards {
 
	public String[] deal(int playerNum, String deck) {
		if (playerNum < 1 || deck == null) {
			return null;
		}
		String[] results = new String[playerNum];
		Arrays.fill(results, "");
		int mod = deck.length() % playerNum;
		for (int i = 0; i < deck.length() - mod; i++) {
			int playerId = i % playerNum;
			results[playerId] += deck.charAt(i);
		}
		return results;
	}
}

CardsTest.java

import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.nullValue;
import static org.junit.Assert.assertThat;
 
import org.junit.Test;
import org.junit.experimental.theories.DataPoints;
import org.junit.experimental.theories.Theories;
import org.junit.experimental.theories.Theory;
import org.junit.runner.RunWith;
 
@RunWith(Theories.class)
public class CardsTest {
	@DataPoints
	public static Fixture[] DATAS = new Fixture[] {
			new Fixture(6, "012345012345012345",
					new String[] { "000", "111", "222", "333", "444", "555" }),
			new Fixture(4, "111122223333", new String[] { "123", "123", "123", "123" }),
			new Fixture(1, "012345012345012345", new String[] { "012345012345012345" }),
			new Fixture(6, "01234", new String[] { "", "", "", "", "", "" }),
			new Fixture(2, "", new String[] { "", "" }), };
 
	@Theory
	public void testDeal(Fixture f) {
		Cards sut = new Cards();
		String[] actual = sut.deal(f.playerNum, f.deck);
		assertThat(actual, is(f.expected));
	}
 
	@Test
	public void testDealForEmpty() {
		Cards sut = new Cards();
		String[] actual = sut.deal(0, "1234");
		assertThat(actual, is(nullValue()));
 
		String[] actual2 = sut.deal(1, null);
		assertThat(actual2, is(nullValue()));
	}
 
	static class Fixture {
		final int playerNum;
		final String deck;
		final String[] expected;
 
		public Fixture(int playerNum, String deck, String[] expected) {
			this.playerNum = playerNum;
			this.deck = deck;
			this.expected = expected;
		}
	}
}