OcpPotterTester.java

import static org.junit.Assert.*;
import org.junit.Test;

public class OcpPotterTester {

	private double price(int... books) {
		Basket basket = new BasketFactory().create();
		return basket.bestPrice(books);
	}

	@Test
	public void testBuyingOneTitle() {
	  assertEquals(0, price(), 0.0);
	  assertEquals(8, price(0), 0.0);
	  assertEquals(8, price(1), 0.0);
	  assertEquals(8, price(2), 0.0);
	  assertEquals(8, price(3), 0.0);
	  assertEquals(8, price(4), 0.0);
	  assertEquals(8 * 2, price(0, 0), 0.0);
	  assertEquals(8 * 3, price(1, 1, 1), 0.0);
	}

	@Test
	public void testDiscountsForSeveralTitles() {
	  assertEquals(8 * 2 * 0.95, price(0, 1), 0.0);
	  assertEquals(8 * 3 * 0.9, price(0, 2, 4), 0.0);
	  assertEquals(8 * 4 * 0.8, price(0, 1, 2, 4), 0.0);
	  assertEquals(8 * 5 * 0.75, price(0, 1, 2, 3, 4), 0.0);
	}
	
	@Test
	public void testSeveralSetsOfBooks() {
		assertEquals(8 + (8 * 2 * 0.95), price(0, 0, 1), 0.0);
		assertEquals(2 * (8 * 2 * 0.95), price(0, 0, 1, 1), 0.0);
		assertEquals((8 * 4 * 0.8) + (8 * 2 * 0.95), price(0, 0, 1, 2, 2, 3), 0.0);
		assertEquals(8 + (8 * 5 * 0.75), price(0, 1, 1, 2, 3, 4), 0.0);
	}

	@Test
	public void testEdgeCases() {
	  assertEquals(2 * (8 * 4 * 0.8), price(0, 0, 1, 1, 2, 2, 3, 4), 0.0);
	  assertEquals(3 * (8 * 5 * 0.75) + 2 * (8 * 4 * 0.8), 
	    price(0, 0, 0, 0, 0, 
	           1, 1, 1, 1, 1, 
	           2, 2, 2, 2, 
	           3, 3, 3, 3, 3, 
	           4, 4, 4, 4), 0.0);
	}
	
}