reimplement and fix unit tests in the largest series product feature

Signed-off-by: xinri <hlay.fr@gmail.com>

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

@@ -129,8 +129,8 @@ public void testSeriesLengthLongerThanLengthOfStringToTestIsRejected() {
 
     @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)