diff --git a/tests/data/base_file.csv b/tests/data/base_file.csv
new file mode 100644
index 0000000..5339ea1
--- /dev/null
+++ b/tests/data/base_file.csv
@@ -0,0 +1,20 @@
+network,is_valid,is_subnet_of_extra
+127.0.0.0/17,FALSE,FALSE
+0.128.0.0/10,TRUE,FALSE
+206.0.0.0/8,TRUE,FALSE
+105.231.36.0/23,TRUE,FALSE
+108.232.0.0/13,TRUE,FALSE
+110.204.32.0/21,TRUE,FALSE
+113.53.128.0/17,TRUE,FALSE
+121.128.0.0/9,TRUE,FALSE
+122.64.0.0/11,TRUE,FALSE
+131.128.0.0/9,TRUE,FALSE
+138.232.0.0/13,TRUE,FALSE
+140.210.168.0/22,TRUE,FALSE
+145.224.0.0/13,TRUE,FALSE
+152.128.0.0/9,TRUE,FALSE
+162.55.64.0/18,TRUE,FALSE
+165.128.0.0/13,TRUE,FALSE
+174.160.0.0/11,TRUE,FALSE
+109.92.213.0/24,TRUE,FALSE
+244.20.0.0/14,TRUE,FALSE
diff --git a/tests/data/extra_file.csv b/tests/data/extra_file.csv
new file mode 100644
index 0000000..0ff7399
--- /dev/null
+++ b/tests/data/extra_file.csv
@@ -0,0 +1,21 @@
+network,is_valid,is_subnet_of_base
+2.11.76.0/22,TRUE,FALSE
+115.7.192.0/19,TRUE,FALSE
+12.132.80.0/20,TRUE,FALSE
+82.64.0.0/11,TRUE,FALSE
+194.48.0.0/17,TRUE,FALSE
+197.216.136.0/21,TRUE,FALSE
+249.0.0.0/9,TRUE,FALSE
+32.17.64.0/20,TRUE,FALSE
+38.66.0.0/17,TRUE,FALSE
+40.240.124.0/22,TRUE,FALSE
+44.26.0.0/19,TRUE,FALSE
+46.99.64.0/20,TRUE,FALSE
+55.48.0.0/15,TRUE,FALSE
+74.0.0.0/10,TRUE,FALSE
+77.120.136.0/22,TRUE,FALSE
+131.128.58.0/23,TRUE,TRUE
+244.20.240.0/20,TRUE,TRUE
+108.232.0.0/16,TRUE,TRUE
+122.68.0.0/14,TRUE,TRUE
+121.128.0.0/10,TRUE,TRUE
diff --git a/tests/merge_test.py b/tests/merge_test.py
index 73254ca..796498e 100644
--- a/tests/merge_test.py
+++ b/tests/merge_test.py
@@ -1,6 +1,9 @@
+"""
+Test merging multiple sets of networks, as if they were independent AS files.
+"""
 from kartograf.merge import general_merge
 
-from .generate_data import (
+from .util.generate_data import (
     build_file_lines,
     generate_ip_file,
     generate_file_items,
@@ -13,6 +16,45 @@
 def __tmp_paths(tmp_path):
     return [tmp_path / p for p in ["rpki_final.txt", "irr_final.txt", "out.txt"]]
 
+def __read_test_vectors(filepath):
+    """
+    Fixtures for IP networks are under tests/data.
+    Read them and return the list of valid networks and the count of individual subnets expected in the result of the merge.
+    """
+    networks = []
+    subnet_count = 0
+    with open(filepath, "r") as f:
+        lines = f.readlines()[1:]
+        for line in lines:
+            network, is_valid, is_subnet = line.split(',')
+            if is_valid == "TRUE":
+                networks.append(network)
+            if is_subnet.strip() == "TRUE":
+                subnet_count += 1
+    return networks, subnet_count
+
+def test_merge_from_fixtures(tmp_path):
+    '''
+    Assert that general_merge merges subnets correctly.
+    '''
+
+    base_nets, base_subnet_count = __read_test_vectors("tests/data/base_file.csv")
+    base_path = tmp_path / "base.txt"
+    extra_nets, extra_subnet_count = __read_test_vectors("tests/data/extra_file.csv")
+    extra_path = tmp_path / "extra.txt"
+    # write the networks to disk, generating ASNs for each network
+    generate_ip_file(base_path, build_file_lines(base_nets, generate_asns(len(base_nets))))
+    generate_ip_file(extra_path, build_file_lines(extra_nets, generate_asns(len(extra_nets))))
+
+    outpath = tmp_path / "final_result.txt"
+    general_merge(base_path, extra_path, None, outpath)
+    with open(outpath, "r") as f:
+        l = f.readlines()
+        final_network_count = len(l)
+        expected_count = (len(base_nets) + len(extra_nets)) - (base_subnet_count + extra_subnet_count)
+        assert final_network_count == expected_count
+
+
 def test_merge(tmp_path):
     """
     Assert that merging two identical files is a no-op.
diff --git a/tests/generate_data.py b/tests/util/generate_data.py
similarity index 100%
rename from tests/generate_data.py
rename to tests/util/generate_data.py
diff --git a/tests/test_util.py b/tests/util_test.py
similarity index 100%
rename from tests/test_util.py
rename to tests/util_test.py