From 7fa573334f7e92baa6adaae83bd1757f3ea61202 Mon Sep 17 00:00:00 2001
From: Humza Shahid <humzasaur@gmail.com>
Date: Sat, 7 Feb 2026 00:33:29 +0000
Subject: [PATCH] add failing test for PersistentVector.extendExistingMatch.
 (Need to fix.)

---
 test/persistent-vector-tests.sml | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/test/persistent-vector-tests.sml b/test/persistent-vector-tests.sml
index 3c61f1c..0dfeab2 100644
--- a/test/persistent-vector-tests.sml
+++ b/test/persistent-vector-tests.sml
@@ -592,6 +592,31 @@ struct
            in
              Expect.isTrue (outputList = expectedOutput)
            end)
+    , test
+        "removes all subsequent elements when new 'finish' is greater \
+        \than any finish in the vector"
+        (fn _ =>
+           let
+             (* arrange *)
+             val inputList = List.tabulate (500, fn i =>
+               {start = i, finish = i})
+             val pv = PersistentVector.fromList inputList
+
+             (* act *)
+             val pv = PersistentVector.extendExistingMatch (5, 999, pv)
+
+             (* assert *)
+             val outputList = PersistentVector.toList pv
+             val expectedOutput =
+               [ {start = 1, finish = 1}
+               , {start = 2, finish = 2}
+               , {start = 3, finish = 3}
+               , {start = 4, finish = 4}
+               , {start = 5, finish = 999}
+               ]
+           in
+             Expect.isTrue (outputList = expectedOutput)
+           end)
     ]
 
   val tests =