diff --git a/test/unit_tests/image_stitcher_test.py b/test/unit_tests/image_stitcher_test.py
index 8e18f67..fa85f69 100644
--- a/test/unit_tests/image_stitcher_test.py
+++ b/test/unit_tests/image_stitcher_test.py
@@ -38,6 +38,13 @@ def make_coord_getter(c):
     }[c]
 
 
+def make_pair_merger(direction):
+    return {
+        "y": merge_pair_vertically,
+        "x": merge_pair_horizontally
+    }[direction]
+
+
 def make_length_getter(dim):
     return {
         "width": make_getter(Info.WIDTH),
@@ -126,20 +133,24 @@ class Stitcher:
         groups = map(merge_group, groups)
 
 
-def merge_group(group):
+def merge_group(group, direction="y"):
 
     def merge_with(aggregation_pair, pairs):
 
-        def aggregate_on_head(pairs_aggr: Iterable[ImageMetadataPair], pair: ImageMetadataPair):
-            """Keeps the image that is being merged with as the head and aggregates non-mergables in the tail"""
+        def merge_on_head_and_aggregate_in_tail(pairs_aggr: Iterable[ImageMetadataPair], pair: ImageMetadataPair):
+            """Keeps the image that is being merged with as the head and aggregates non-mergables in the tail."""
             aggr, non_aggr = juxt(first, rest)(pairs_aggr)
-            if y2_getter(aggr) == y1_getter(pair):
-                aggr = merge_pair_vertically(aggr, pair)
+            if c2_getter(aggr) == c1_getter(pair):
+                aggr = pair_merger(aggr, pair)
                 return aggr, *non_aggr
             else:
                 return aggr, pair, *non_aggr
 
-        return list(reduce(aggregate_on_head, pairs, [aggregation_pair]))
+        return list(reduce(merge_on_head_and_aggregate_in_tail, pairs, [aggregation_pair]))
+
+    c1_getter = make_coord_getter(f"{direction}1")
+    c2_getter = make_coord_getter(f"{direction}2")
+    pair_merger = make_pair_merger(direction)
 
     pairs = list(group)