From 7f61b01600ecbdaa2a57c51097f2ece9e421c4fe Mon Sep 17 00:00:00 2001
From: Silvan Mosberger <silvan.mosberger@tweag.io>
Date: Fri, 14 Jul 2023 19:26:08 +0200
Subject: lib.lists.commonPrefix: init

---
 lib/tests/misc.nix | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

(limited to 'lib/tests/misc.nix')

diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix
index dfa6a94ee48e..ab97409d8567 100644
--- a/lib/tests/misc.nix
+++ b/lib/tests/misc.nix
@@ -488,6 +488,39 @@ runTests {
     expected = { a = [ 2 3 ]; b = [7]; c = [8];};
   };
 
+  testListCommonPrefixExample1 = {
+    expr = lists.commonPrefix [ 1 2 3 4 5 6 ] [ 1 2 4 8 ];
+    expected = [ 1 2 ];
+  };
+  testListCommonPrefixExample2 = {
+    expr = lists.commonPrefix [ 1 2 3 ] [ 1 2 3 4 5 ];
+    expected = [ 1 2 3 ];
+  };
+  testListCommonPrefixExample3 = {
+    expr = lists.commonPrefix [ 1 2 3 ] [ 4 5 6 ];
+    expected = [ ];
+  };
+  testListCommonPrefixEmpty = {
+    expr = lists.commonPrefix [ ] [ 1 2 3 ];
+    expected = [ ];
+  };
+  testListCommonPrefixSame = {
+    expr = lists.commonPrefix [ 1 2 3 ] [ 1 2 3 ];
+    expected = [ 1 2 3 ];
+  };
+  testListCommonPrefixLazy = {
+    expr = lists.commonPrefix [ 1 ] [ 1 (abort "lib.lists.commonPrefix shouldn't evaluate this")];
+    expected = [ 1 ];
+  };
+  # This would stack overflow if `commonPrefix` were implemented using recursion
+  testListCommonPrefixLong =
+    let
+      longList = genList (n: n) 100000;
+    in {
+      expr = lists.commonPrefix longList longList;
+      expected = longList;
+    };
+
   testSort = {
     expr = sort builtins.lessThan [ 40 2 30 42 ];
     expected = [2 30 40 42];
-- 
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