TDDBC_Fukuoka_FizzBuzz

package tddbc;

import static org.junit.Assert.*;
import static org.hamcrest.CoreMatchers.*;

import java.util.ArrayList;
import java.util.List;

import org.junit.Test;

public class FizzBuzzTest {

	@Test
	public void 三はFizz() throws Exception {
		String result = fizzBuzz(3);
		assertThat(result, is("Fizz"));
	}

	@Test
	public void 三の倍数はFizz() throws Exception {
		String result = fizzBuzz(6);
		assertThat(result, is("Fizz"));
	}

	@Test
	public void 五はBuzz() throws Exception {
		String result = fizzBuzz(5);
		assertThat(result, is("Buzz"));
	}

	@Test
	public void 五の倍数はBuzz() throws Exception {
		String result = fizzBuzz(250);
		assertThat(result, is("Buzz"));

		result = fizzBuzz(260);
		assertThat(result, is("Buzz"));
	}

	@Test(expected = IllegalArgumentException.class)
	public void 零の場合例外() throws Exception {
		fizzBuzz(0);
	}

	@Test(expected = IllegalArgumentException.class)
	public void マイナス値も例外() throws Exception {
		fizzBuzz(-15);
	}

	@Test
	public void 一の場合1を返す() {
		String result = fizzBuzz(1);
		assertThat(result, is("1"));
	}

	@Test
	public void 三の倍数でも五の倍数でもない() throws Exception {
		String result = fizzBuzz(13);
		assertThat(result, is("13"));
	}

	@Test
	public void 十五はFizzBuzz() throws Exception {
		String result = fizzBuzz(15);
		assertThat(result, is("FizzBuzz"));
	}

	@Test
	public void 十五の倍数はFizzBuzz() throws Exception {
		String result = fizzBuzz(1500);
		assertThat(result, is("FizzBuzz"));
	}

	@Test
	public void 閉区間のFizzBuzz_同じ数字() throws Exception {
		List<String> result = fizzBuzz(1, 1);
		assertThat(result, is(notNullValue()));
		assertThat(result.size(), is(1));
		assertThat(result.get(0), is("1"));
	}

	@Test
	public void 閉区間のFizzBuzz() throws Exception {
		List<String> result = fizzBuzz(1, 10);
		assertThat(result, is(notNullValue()));
		assertThat(result.size(), is(10));
		assertThat(result.get(0), is("1"));
		assertThat(result.get(1), is("2"));
		assertThat(result.get(2), is("Fizz"));
		assertThat(result.get(3), is("4"));
		assertThat(result.get(4), is("Buzz"));
		assertThat(result.get(5), is("Fizz"));
		assertThat(result.get(6), is("7"));
		assertThat(result.get(7), is("8"));
		assertThat(result.get(8), is("Fizz"));
		assertThat(result.get(9), is("Buzz"));
	}

	@Test(expected = IllegalArgumentException.class)
	public void 閉区間のFizzBuzz_第一引数より第二引数のほうが小さい() throws Exception {
		fizzBuzz(6, 1);
	}

	private List<String> fizzBuzz(int i, int j) {
		if (j < i) throw new IllegalArgumentException();
		List<String> list = new ArrayList<String>();
		for (int k = i; k <= j; k++)
			list.add(fizzBuzz(k));
		return list;
	}

	private String fizzBuzz(int n) {
		if (n < 1) throw new IllegalArgumentException();

		StringBuilder s = new StringBuilder();
		if (n % 3 == 0) s.append("Fizz");
		if (n % 5 == 0) s.append("Buzz");
		if (s.length() == 0) s.append(n);

		return s.toString();
	}

}