diff --git a/src/test/java/com/shoonya/BillingServiceTest.java b/src/test/java/com/shoonya/BillingServiceTest.java
index 168f81b..3b77a1a 100644
--- a/src/test/java/com/shoonya/BillingServiceTest.java
+++ b/src/test/java/com/shoonya/BillingServiceTest.java
@@ -25,6 +25,13 @@ void roundsLineTotalToTwoDecimalPlaces() {
         assertEquals(new BigDecimal("10.01"), result);
     }
 
+    @Test
+    void calculatesZeroPricedLineTotal() {
+        BigDecimal result = billingService.calculateLineTotal(BigDecimal.ZERO, 3);
+
+        assertEquals(new BigDecimal("0.00"), result);
+    }
+
     @Test
     void rejectsNonPositiveQuantity() {
         assertThrows(IllegalArgumentException.class,