diff --git a/tests/test_metadata_serialization.py b/tests/test_metadata_serialization.py
index 9f228d4c8f..0f5ebb8975 100644
--- a/tests/test_metadata_serialization.py
+++ b/tests/test_metadata_serialization.py
@@ -168,6 +168,25 @@ def test_role_serialization(self, test_case_data: str):
             "keys": {"keyid" : {"keytype": "rsa", "scheme": "rsassa-pss-sha256", "keyval": {"public": "foo"}}}, \
             "roles": { "targets": {"keyids": ["keyid"], "threshold": 3}}, \
             "foo": "bar"}',
+        "many keys": '{"_type": "root", "spec_version": "1.0.0", "version": 1, \
+            "expires": "2030-01-01T00:00:00Z", "consistent_snapshot": false, \
+            "keys": { \
+                "keyid1" : {"keytype": "rsa", "scheme": "rsassa-pss-sha256", "keyval": {"public": "foo"}}, \
+                "keyid2" : {"keytype": "ed25519", "scheme": "ed25519", "keyval": {"public": "bar"}}}, \
+            "roles": { "targets": {"keyids": ["keyid"], "threshold": 3}} \
+            }',
+        "many roles": '{"_type": "root", "spec_version": "1.0.0", "version": 1, \
+            "expires": "2030-01-01T00:00:00Z", "consistent_snapshot": false, \
+            "keys": {"keyid" : {"keytype": "rsa", "scheme": "rsassa-pss-sha256", "keyval": {"public": "foo"}}}, \
+            "roles": { \
+                "targets": {"keyids": ["keyid1"], "threshold": 1}, \
+                "snapshot": {"keyids": ["keyid2"], "threshold": 1}} \
+            }',
+        "many role keyids": '{"_type": "root", "spec_version": "1.0.0", "version": 1, \
+            "expires": "2030-01-01T00:00:00Z", "consistent_snapshot": false, \
+            "keys": {"keyid" : {"keytype": "rsa", "scheme": "rsassa-pss-sha256", "keyval": {"public": "foo"}}}, \
+            "roles": {"targets": {"keyids": ["keyid1", "keyid2"], "threshold": 3}} \
+            }',
     }
 
     @run_sub_tests_with_dataset(valid_roots)
@@ -184,6 +203,7 @@ def test_root_serialization(self, test_case_data: str):
         "empty hashes dict": '{"version": 1, "length": 1, "hashes": {}}',
         "hashes wrong type": '{"version": 1, "length": 1, "hashes": 1}',
         "hashes values wrong type": '{"version": 1, "length": 1, "hashes": {"sha256": 1}}',
+        "zero hashes": '{"version": 1, "length": 1, "hashes": {}}',
     }
 
     @run_sub_tests_with_dataset(invalid_metafiles)
@@ -198,6 +218,7 @@ def test_invalid_metafile_serialization(self, test_case_data: Dict[str, str]):
         "no length": '{"hashes": {"sha256" : "abc"}, "version": 1 }',
         "no hashes": '{"length": 12, "version": 1}',
         "unrecognized field": '{"hashes": {"sha256" : "abc"}, "length": 12, "version": 1, "foo": "bar"}',
+        "many hashes": '{"hashes": {"sha256" : "abc", "sha512": "cde"}, "length": 12, "version": 1}',
     }
 
     @run_sub_tests_with_dataset(valid_metafiles)
@@ -246,6 +267,9 @@ def test_snapshot_serialization(self, test_case_data: str):
             '{"keyids": ["keyid"], "name": "a", "terminating": true, "threshold": 3}',
         "unrecognized field":
             '{"keyids": ["keyid"], "name": "a", "terminating": true, "threshold": 3, "foo": "bar"}',
+        "many keyids":
+            '{"keyids": ["keyid1", "keyid2"], "name": "a", "paths": ["fn1", "fn2"], \
+            "terminating": false, "threshold": 1}',
     }
 
     @run_sub_tests_with_dataset(valid_delegated_roles)
@@ -262,6 +286,12 @@ def test_delegated_role_serialization(self, test_case_data: str):
             '{"keys": {"keyid" : {"keytype": "rsa", "scheme": "rsassa-pss-sha256", "keyval": {"public": "foo"}}}, \
             "roles": [ {"keyids": ["keyid"], "name": "a", "terminating": true, "threshold": 3} ], \
             "foo": "bar"}',
+        "many keys":
+            '{"keys": { \
+                "keyid1" : {"keytype": "rsa", "scheme": "rsassa-pss-sha256", "keyval": {"public": "foo"}}, \
+                "keyid2" : {"keytype": "ed25519", "scheme": "ed25519", "keyval": {"public": "bar"}}}, \
+            "roles": [ {"keyids": ["keyid"], "name": "a", "terminating": true, "threshold": 3} ] \
+            }',
     }
 
     @run_sub_tests_with_dataset(valid_delegations)