Only calculate the optimal test split on the first index

Author: Donnerbart

src/main/java/de/donnerbart/split/TestSplitMain.java

@@ -100,6 +100,10 @@ static int calculateOptimalTotalSplit(final @NotNull Arguments arguments, final
             LOG.warn("The option --calculate-optimal-total-split requires --junit-glob");
             return 0;
         }
+        if (arguments.splitIndex != 0) {
+            LOG.debug("Skipping calculation of optimal test split (only done on the first index)");
+            return 0;
+        }
         LOG.info("Calculating optimal test split");
         var optimalSplit = 1;
         var lastSlowestSplit = Double.MAX_VALUE;

src/test/java/de/donnerbart/split/TestSplitMainTest.java

@@ -152,4 +152,10 @@ void calculateOptimalTotalSplit_withoutJUnitGlob() throws Exception {
         jCommander.parse("-i", "0", "-t", "1", "-g", "**/*Test.java");
         assertThat(TestSplitMain.calculateOptimalTotalSplit(arguments, tmp)).isEqualTo(0);
     }
+
+    @Test
+    void calculateOptimalTotalSplit_withInvalidSplitIndex() throws Exception {
+        jCommander.parse("-i", "1", "-t", "1", "-g", "**/*Test.java", "-j", "**/junit-reports/*.xml");
+        assertThat(TestSplitMain.calculateOptimalTotalSplit(arguments, tmp)).isEqualTo(0);
+    }
 }