reimplement and fix unit tests in the largest series product feature

Signed-off-by: xinri <[email protected]>

Author: xinri

exercises/practice/largest-series-product/.meta/config.json

@@ -22,6 +22,7 @@
     "Smarticles101",
     "sonapraneeth-a",
     "sshine",
+    "Xinri",
     "Zaldrick"
   ],
   "files": {

exercises/practice/largest-series-product/src/test/java/LargestSeriesProductCalculatorTest.java

@@ -124,18 +124,18 @@ public void testSeriesLengthLongerThanLengthOfStringToTestIsRejected() {
 
         assertThatExceptionOfType(IllegalArgumentException.class)
                 .isThrownBy(() -> calculator.calculateLargestProductForSeriesLength(4))
-                .withMessage("Series length must be less than or equal to the length of the string to search.");
+                .withMessage("Series length must not exceed the length of the string to search.");
     }
 
     @Disabled("Remove to run test")
     @Test
-    @DisplayName("reports 1 for empty string and empty product (0 span)")
-    public void testEmptyStringToSearchAndSeriesOfNonZeroLengthIsRejected() {
+    @DisplayName("rejects empty string and nonzero span")
+    public void testEmptyStringAndNonZeroSpanIsRejected() {
         LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("");
 
         assertThatExceptionOfType(IllegalArgumentException.class)
                 .isThrownBy(() -> calculator.calculateLargestProductForSeriesLength(1))
-                .withMessage("Series length must be less than or equal to the length of the string to search.");
+                .withMessage("Series length must not exceed the length of the string to search.");
     }
 
     @Disabled("Remove to run test")
@@ -155,7 +155,7 @@ public void testNegativeSeriesLengthIsRejected() {
 
         assertThatExceptionOfType(IllegalArgumentException.class)
                 .isThrownBy(() -> calculator.calculateLargestProductForSeriesLength(-1))
-                .withMessage("Series length must be non-negative.");
+                .withMessage("Series length must not be negative.");
     }
 
     @Disabled("Remove to run test")