diff --git a/lib/iris/tests/graphics/__init__.py b/lib/iris/tests/graphics/__init__.py
index 2ef635128e..a083de3934 100755
--- a/lib/iris/tests/graphics/__init__.py
+++ b/lib/iris/tests/graphics/__init__.py
@@ -57,9 +57,9 @@
 _lock = threading.Lock()
 
 #: Default perceptual hash size.
-_HASH_SIZE = 16
+HASH_SIZE = 16
 #: Default maximum perceptual hash hamming distance.
-_HAMMING_DISTANCE = 2
+HAMMING_DISTANCE = 2
 # Prefix for image test results (that aren't yet verified as good to add to
 # reference images)
 RESULT_PREFIX = "result-"
@@ -135,7 +135,7 @@ def get_phash(input: Path) -> str:
     from PIL import Image
     import imagehash
 
-    return imagehash.phash(Image.open(input), hash_size=_HASH_SIZE)
+    return imagehash.phash(Image.open(input), hash_size=HASH_SIZE)
 
 
 def generate_repo_from_baselines(baseline_image_dir: Path) -> Dict[str, str]:
@@ -220,7 +220,7 @@ def _create_missing(phash: str) -> None:
             # Calculate hamming distance vector for the result hash.
             distance = expected - phash
 
-            if distance > _HAMMING_DISTANCE:
+            if distance > HAMMING_DISTANCE:
                 if dev_mode:
                     _create_missing(phash)
                 else:
diff --git a/lib/iris/tests/graphics/recreate_imagerepo.py b/lib/iris/tests/graphics/recreate_imagerepo.py
index 756e48688d..02ddaad2cb 100755
--- a/lib/iris/tests/graphics/recreate_imagerepo.py
+++ b/lib/iris/tests/graphics/recreate_imagerepo.py
@@ -29,9 +29,9 @@ def update_json(baseline_image_dir: Path, dry_run: bool = False):
         )
         print(msg)
     else:
-        for key in set(repo.keys()) | set(suggested_repo.keys()):
-            old_val = repo.get(key, None)
-            new_val = suggested_repo.get(key, None)
+        for key in sorted(set(repo.keys()) | set(suggested_repo.keys())):
+            old_val = repo.get(key)
+            new_val = suggested_repo.get(key)
             if old_val is None:
                 repo[key] = suggested_repo[key]
                 print(key)