Add 2 tests for merge indexes

src/commonTest/kotlin/testMerge.kt

@@ -1,4 +1,5 @@
 import net.sergeych.merge3.MergeResult
+import net.sergeych.merge3.MergedBlock
 import net.sergeych.merge3.merge3
 import net.sergeych.mp_logger.Log
 import net.sergeych.sprintf.sprintf
@@ -74,4 +75,30 @@ class BasicTest {
         println(m.changedAreas)
         assertEquals("Hello 123456", m.merged.str)
     }
+
+    @Test
+    fun testMergeIndexes() {
+        Log.connectConsole()
+        val src = "Hello".toList()
+        val a = "123 Hello".toList()
+        val b = "456 Hello".toList()
+
+        val m = merge3(src, b, a, true)
+        val unchanged = m.blocks.last() as MergedBlock.Unchanged
+        println(unchanged)
+        assertEquals(0, unchanged.referenceIndex)
+    }
+
+    @Test
+    fun testMergeIndexes2() {
+        Log.connectConsole()
+        val src = "Hello".toList()
+        val a = "1Hello".toList()
+        val b = "2Hello".toList()
+
+        val m = merge3(src, b, a, true)
+        val unchanged = m.blocks.last() as MergedBlock.Unchanged
+        println(unchanged)
+        assertEquals(0, unchanged.referenceIndex)
+    }
 }