JUnit Help with PriceTest fixture

Question

Consider a grocery market where items have prices per unit but also volume prices. For example, doughnuts may be $1.00 each or 4 for $3 dollars.
public class PriceTest extends TestCase {
     public void testUnitPrice() throws Exception {
          Price price = new Price(7.0);
          assertEquals(14.0, price.calc(2));
     public void testMultiUnitPrice() throws Exception {
          Price price = new Price(1.0, 4, 3.0);
          assertEquals(6.0, price.calc(8));
     public void testCombinedPrice() throws Exception {
          Price price = new Price(1.0, 4, 3.0);
          assertEquals(4.0, price.calc(5));
}Here's my "Object under Test":
public class Price {
     private final double price;
     private final Integer itemsPerPackage;
     private final Double pricePerPackage;
     public Price(double price) {
          this(price, null, null);
     public Price(double price, Integer itemsPerPackage, Double pricePerPackage) {
          this.price = price;
          this.itemsPerPackage = itemsPerPackage;
          this.pricePerPackage = pricePerPackage;
     public double calc(int count) {
          if (pricePerPackage != null) {
               return pricePerPackage * count / itemsPerPackage;
          } else {
               return price * count;
}My first two tests work inside PriceTest, but my testCombinedPrice() method throws the following error:
junit.framework.AssertionFailedError: expected:<4.0> but was:<3.75>
What can I change in the Price#calc() method to make the failing testCombinedPrice() work?

Answer 1

Thanks for responding, Wiraj,
The count should be seen as the "item count" so it needs to be declared as an integer...
The use case is four doughnuts are given for $3.00 plus the extra doughnut which is given for $1.00. The combined price is then $3.00 + $1.00 = $4.00 not $3.75.
Obviously, its something inside the Price#calc() method which has to be altered but I need all the tests to work (including testMultiUnitPrice() and testCombinedPrice() methods).
Is there a way to change Price#calc() method to work for both tests?
Happy coding.