bookstore: fix test suite equality checks

exercises/book-store/src/example/java/Bookstore.java

@@ -1,61 +1,57 @@
-import java.awt.print.Printable;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Collectors;
 
-public class Bookstore{
+class Bookstore {
 
-	private static int BOOK_PRICE = 8, MAX_GROUP_SIZE = 5;
-	private List<Integer> books;
-	private static double[] DISCOUNT_TIERS = {0,5,10,20,25};   	
+  private static final int BOOK_PRICE = 8, MAX_GROUP_SIZE = 5;
 
-	public Bookstore (List<Integer> books){
-		this.books = books;
-	}	
-	
+  private static double[] DISCOUNT_TIERS = {0, 5, 10, 20, 25};
 
+  private List<Integer> books;
 
+  Bookstore(List<Integer> books) {
+    this.books = books;
+  }
 
-	public double calculateTotalCost(){
-		return calculateTotalCost(this.books,0);
-	}
+  double calculateTotalCost() {
+    return calculateTotalCost(this.books, 0);
+  }
 
-	private double calculateTotalCost (List<Integer> books,double priceSoFar ){
-		double minPrice = Double.MAX_VALUE;
+  private double calculateTotalCost(List<Integer> books, double priceSoFar) {
+    if (books.size() == 0) {
+      return priceSoFar;
+    }
 
+    List<Integer> availableBookNumbers = books.stream()
+        .distinct()
+        .collect(Collectors.toList());
 
-		if(books.size() == 0){
-			return priceSoFar;
-		}
+    double minPrice = Double.MAX_VALUE;
 
-		List<Integer> groups = (ArrayList<Integer>) books.stream().distinct().collect(Collectors.toList());
+    for (int i = 0; i < availableBookNumbers.size(); i++) {
+      List<Integer> newGroupBooks = new ArrayList<>(availableBookNumbers.subList(0, i + 1));
+      List<Integer> remainingBooks = new ArrayList<>(books);
 
-		
-		double price = 0;
+      for (final Integer newGroupBook : newGroupBooks) {
+        //noinspection UseBulkOperation - we want to remove _one_ of each book number, not _all_ of each book number.
+        remainingBooks.remove(newGroupBook);
+      }
 
-		for(int i = 0;i<groups.size();i++){
-			books.remove(groups.get(i));	
-		}
-				
-		try {
-			price = calculateTotalCost(books,priceSoFar + costPerGroup(groups.size()));
-		} catch (Exception e) {
-			e.printStackTrace();
-		}
-		
-		minPrice = Math.min(minPrice, price);
-		return minPrice;
+      double price = calculateTotalCost(remainingBooks, priceSoFar + costOfGroupSize(newGroupBooks.size()));
 
+      minPrice = Math.min(minPrice, price);
+    }
 
-	}
+    return minPrice;
+  }
 
-	private double costPerGroup(int groupSize) throws Exception{
-		if (groupSize < 1 || groupSize > MAX_GROUP_SIZE){
-        		throw new Exception("Invalid group size : " + groupSize );
-     		}
-    		return BOOK_PRICE * groupSize * (100 - DISCOUNT_TIERS[groupSize-1])/100;
-	}
+  private double costOfGroupSize(int groupSize) {
+    if (groupSize < 1 || groupSize > MAX_GROUP_SIZE) {
+      throw new IllegalStateException("Invalid group size : " + groupSize);
+    }
 
+    return BOOK_PRICE * groupSize * (100 - DISCOUNT_TIERS[groupSize - 1]) / 100;
+  }
 
 }

exercises/book-store/src/test/java/BookstoreTest.java

@@ -1,5 +1,6 @@
 import static org.junit.Assert.assertEquals;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -7,112 +8,112 @@ import java.util.Arrays;
 import org.junit.Ignore;
 import org.junit.Test;
 
-public class BookstoreTest{
-
-	@Test
-	public void onlyASingleBook(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(8,bookstore.calculateTotalCost(),2);
-	}
-	
-	@Ignore
-	@Test
-	public void twoOfSameBook(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(16,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void emptyBasket(){
-		List<Integer> books = new ArrayList<>();
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(0,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void twoDifferentBooks(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,2));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(15.20,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void threeDifferentBooks(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,2,3));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(21.6,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void fourDifferentBooks(){
-		ArrayList<Integer> books = new ArrayList<>(Arrays.asList(1,2,3,4));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(25.6,bookstore.calculateTotalCost(),2);
-
-	}
-
-	@Ignore
-	@Test
-	public void fiveDifferentBooks(){
-		ArrayList<Integer> books = new ArrayList<>(Arrays.asList(1,2,3,4,5));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(30,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void twoGroupsOfFourIsCheaperThanGroupOfFivePlusGroupOfThree(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1,2,2,3,3,4,5));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(51.20,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void groupOfFourPlusGroupOfTwoIsCheaperThanTwoGroupsOfThree(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1,2,2,3,4));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(40.8,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void twoEachOfFirst4BooksAnd1CopyEachOfRest(){
-		Integer[] p = {1,1,2,2,3,3,4,4,5};
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1,2,2,3,3,4,4,5));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(55.60,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void twoCopiesOfEachBook(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1,2,2,3,3,4,4,5,5));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(60.00,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void threeCopiesOfFirstBookAnd2EachOfRemaining(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1,2,2,3,3,4,4,5,5,1));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(68.00,bookstore.calculateTotalCost(),2);
-	}
-
-	@Ignore
-	@Test
-	public void threeEachOFirst2BooksAnd2EachOfRemainingBooks(){
-		List<Integer> books = new ArrayList<>(Arrays.asList(1,1,2,2,3,3,4,4,5,5,1,2));
-		Bookstore bookstore = new Bookstore(books);
-		assertEquals(75.20,bookstore.calculateTotalCost(),2);
-	}
+public class BookstoreTest {
+
+  // This is sufficient accuracy since we're handling currency values, which should be equal to within 2 decimal places.
+  private static final double EQUALITY_TOLERANCE = 0.001;
+
+  @Test
+  public void onlyASingleBook() {
+    List<Integer> books = new ArrayList<>(Collections.singletonList(1));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(8, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void twoOfSameBook() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(16, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void emptyBasket() {
+    List<Integer> books = new ArrayList<>();
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(0, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void twoDifferentBooks() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 2));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(15.20, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void threeDifferentBooks() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 2, 3));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(21.6, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void fourDifferentBooks() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 2, 3, 4));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(25.6, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void fiveDifferentBooks() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(30, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void twoGroupsOfFourIsCheaperThanGroupOfFivePlusGroupOfThree() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1, 2, 2, 3, 3, 4, 5));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(51.20, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void groupOfFourPlusGroupOfTwoIsCheaperThanTwoGroupsOfThree() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1, 2, 2, 3, 4));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(40.8, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void twoEachOfFirst4BooksAnd1CopyEachOfRest() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(55.60, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void twoCopiesOfEachBook() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5, 5));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(60.00, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void threeCopiesOfFirstBookAnd2EachOfRemaining() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(68.00, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
+
+  @Ignore
+  @Test
+  public void threeEachOFirst2BooksAnd2EachOfRemainingBooks() {
+    List<Integer> books = new ArrayList<>(Arrays.asList(1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 1, 2));
+    Bookstore bookstore = new Bookstore(books);
+    assertEquals(75.20, bookstore.calculateTotalCost(), EQUALITY_TOLERANCE);
+  }
 
 }
-