From bc53e8b7ee615ef77da50d1434102396281cfcdd Mon Sep 17 00:00:00 2001
From: Jakob Keller <57402305+jakob-keller@users.noreply.github.com>
Date: Sun, 16 Feb 2025 21:39:53 +0100
Subject: [PATCH] Lambda: Determine Lambda image deterministically

---
 moto/awslambda/models.py | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/moto/awslambda/models.py b/moto/awslambda/models.py
index de8fc1f13e9d..b51676126112 100644
--- a/moto/awslambda/models.py
+++ b/moto/awslambda/models.py
@@ -1023,13 +1023,11 @@ def _invoke_lambda(self, event: Optional[str] = None) -> Tuple[str, bool, str]:
                     # - lambci/lambda (the repo with older/outdated AWSLambda images
                     #
                     # We'll cycle through all of them - when we find the repo that contains our image, we use it
-                    image_repos = set(
-                        [
-                            settings.moto_lambda_image(),
-                            "mlupin/docker-lambda",
-                            "lambci/lambda",
-                        ]
-                    )
+                    image_repos = {  # dict maintains insertion order
+                        settings.moto_lambda_image(): None,
+                        "mlupin/docker-lambda": None,
+                        "lambci/lambda": None,
+                    }
                     for image_repo in image_repos:
                         image_ref = (
                             image_repo