From e946c7b14adc7a0aaa9ac883de217a3c0e556a81 Mon Sep 17 00:00:00 2001
From: Andrew Murray <3112309+radarhere@users.noreply.github.com>
Date: Fri, 7 Mar 2025 02:42:10 +1100
Subject: [PATCH] Test using _seek to skip frames (#8804)

Co-authored-by: Andrew Murray <radarhere@users.noreply.github.com>
---
 Tests/test_file_apng.py | 5 ++++-
 Tests/test_file_fli.py  | 3 +++
 Tests/test_file_gif.py  | 4 ++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Tests/test_file_apng.py b/Tests/test_file_apng.py
index 9d5154fca..b9a036173 100644
--- a/Tests/test_file_apng.py
+++ b/Tests/test_file_apng.py
@@ -34,8 +34,11 @@ def test_apng_basic() -> None:
         with pytest.raises(EOFError):
             im.seek(2)
 
-        # test rewind support
         im.seek(0)
+        with pytest.raises(ValueError, match="cannot seek to frame 2"):
+            im._seek(2)
+
+        # test rewind support
         assert im.getpixel((0, 0)) == (255, 0, 0, 255)
         assert im.getpixel((64, 32)) == (255, 0, 0, 255)
         im.seek(1)
diff --git a/Tests/test_file_fli.py b/Tests/test_file_fli.py
index 8adbd30f5..8a95af62d 100644
--- a/Tests/test_file_fli.py
+++ b/Tests/test_file_fli.py
@@ -160,6 +160,9 @@ def test_seek() -> None:
 
         assert_image_equal_tofile(im, "Tests/images/a_fli.png")
 
+        with pytest.raises(ValueError, match="cannot seek to frame 52"):
+            im._seek(52)
+
 
 @pytest.mark.parametrize(
     "test_file",
diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index d2592da97..dbbffc675 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -410,6 +410,10 @@ def test_seek() -> None:
         except EOFError:
             assert frame_count == 5
 
+        img.seek(0)
+        with pytest.raises(ValueError, match="cannot seek to frame 2"):
+            img._seek(2)
+
 
 def test_seek_info() -> None:
     with Image.open("Tests/images/iss634.gif") as im: