diff --git a/test/unit_tests/image_stitcher_test.py b/test/unit_tests/image_stitcher_test.py
index 37c6fd5..1896fd9 100644
--- a/test/unit_tests/image_stitcher_test.py
+++ b/test/unit_tests/image_stitcher_test.py
@@ -151,12 +151,8 @@ def make_merger_aggregator(direction):
 
 
 def merge_group(group, direction):
-
     reduce_group = make_merger_aggregator(direction)
-
-    for g1, g2 in chunk_iterable(iterate(reduce_group, group), chunk_size=2):
-        if len(g1) == len(g2):
-            return g1
+    return until_convergence(reduce_group, group)
 
 
 def merge_group_horizontally(group):
@@ -204,20 +200,21 @@ class Stitcher:
 
         return pairs
 
+    def merge_along_both_axes(self, pairs):
+
+        pairs = self.merge_along_axis(pairs, "x")
+        pairs = list(self.merge_along_axis(pairs, "y"))
+
+        return pairs
+
     def stitch(self, pairs: Iterable[ImageMetadataPair]) -> List[ImageMetadataPair]:
+        return until_convergence(self.merge_along_both_axes, pairs)
 
-        pairs = list(pairs)
-        n = len(pairs)
 
-        while True:
-
-            pairs = self.merge_along_axis(pairs, "x")
-            pairs = list(self.merge_along_axis(pairs, "y"))
-
-            if len(pairs) == n:
-                return pairs
-
-            n = len(pairs)
+def until_convergence(func, *args, **kwargs):
+    for a, b in chunk_iterable(iterate(func, *args, **kwargs), chunk_size=2):
+        if len(a) == len(b):
+            return a
 
 
 #####################################