Tests: simplify and shorten test_metadata_eq_.py

There is a lot of repetitive code inside test_metadata_eq_.py.
Remove it by using the decorator.

I am initializing the object instances in setUpClass instead of doing it
inside the test function in order to escape the need for
reinitialization of the instances on each attribute.

Signed-off-by: Martin Vrachev <mvrachev@vmware.com>

Author: Martin Vrachev

tests/test_metadata_eq_.py

@@ -23,11 +23,7 @@
     Metadata,
     MetaFile,
     Role,
-    Root,
-    Snapshot,
     TargetFile,
-    Targets,
-    Timestamp,
 )
 
 
@@ -41,34 +37,76 @@ def setUpClass(cls) -> None:
         cls.repo_dir = os.path.join(
             utils.TESTS_DIR, "repository_data", "repository", "metadata"
         )
-        cls.metadata = {}
+
+        # Store class instances in this dict instead of creating them inside the
+        # test function in order to escape the need for reinitialization of the
+        # instances on each run of the test function.
+        cls.objects = {}
         for md in TOP_LEVEL_ROLE_NAMES:
             with open(os.path.join(cls.repo_dir, f"{md}.json"), "rb") as f:
-                cls.metadata[md] = f.read()
+                data = f.read()
+                cls.objects[md.capitalize()] = Metadata.from_bytes(data).signed
+
+        cls.objects["Metadata"] = Metadata(cls.objects["Timestamp"], {})
+        cls.objects["Signed"] = cls.objects["Timestamp"]
+        cls.objects["Key"] = Key(
+            "id", "rsa", "rsassa-pss-sha256", {"public": "foo"}
+        )
+        cls.objects["Role"] = Role(["keyid1", "keyid2"], 3)
+        cls.objects["MetaFile"] = MetaFile(1, 12, {"sha256": "abc"})
+        cls.objects["DelegatedRole"] = DelegatedRole("a", [], 1, False, ["d"])
+        cls.objects["Delegations"] = Delegations(
+            {"keyid": cls.objects["Key"]}, {"a": cls.objects["DelegatedRole"]}
+        )
+        cls.objects["TargetFile"] = TargetFile(
+            1, {"sha256": "abc"}, "file1.txt"
+        )
+
+    # Keys are class names.
+    # Values are dictionaries containing attribute names and their new values.
+    classes_attributes_modifications: utils.DataSet = {
+        "Metadata": {"signed": None, "signatures": None},
+        "Signed": {"version": -1, "spec_version": "0.0.0"},
+        "Key": {"keyid": "a", "keytype": "foo", "scheme": "b", "keyval": "b"},
+        "Role": {"keyids": [], "threshold": 10},
+        "Root": {"consistent_snapshot": None, "keys": {}},
+        "MetaFile": {"version": None, "length": None, "hashes": {}},
+        "Timestamp": {"snapshot_meta": None},
+        "Snapshot": {"meta": None},
+        "DelegatedRole": {
+            "name": "",
+            "terminating": None,
+            "paths": [""],
+            "path_hash_prefixes": [""],
+        },
+        "Delegations": {"keys": {}, "roles": {}},
+        "TargetFile": {"length": 0, "hashes": {}, "path": ""},
+        "Targets": {"targets": {}, "delegations": []},
+    }
+
+    @utils.run_sub_tests_with_dataset(classes_attributes_modifications)
+    def test_classes_eq_(self, test_case_data: Dict[str, Any]) -> None:
+        obj = self.objects[self.case_name]  # pylint: disable=no-member
 
-    def copy_and_simple_assert(self, obj: Any) -> Any:
         # Assert that obj is not equal to an object from another type
         self.assertNotEqual(obj, "")
-        result_obj = copy.deepcopy(obj)
+        obj_2 = copy.deepcopy(obj)
         # Assert that __eq__ works for equal objects.
-        self.assertEqual(obj, result_obj)
-        return result_obj
-
-    def test_metadata_eq_(self) -> None:
-        md = Metadata.from_bytes(self.metadata["snapshot"])
-        md_2: Metadata = self.copy_and_simple_assert(md)
+        self.assertEqual(obj, obj_2)
 
-        for attr, value in [("signed", None), ("signatures", None)]:
-            setattr(md_2, attr, value)
-            self.assertNotEqual(md, md_2, f"Failed case: {attr}")
+        for attr, value in test_case_data.items():
+            original_value = getattr(obj_2, attr)
+            setattr(obj_2, attr, value)
+            # Assert that the original object != modified one.
+            self.assertNotEqual(obj, obj_2, f"Failed case: {attr}")
             # Restore the old value of the attribute.
-            setattr(md_2, attr, getattr(md, attr))
+            setattr(obj_2, attr, original_value)
 
     def test_md_eq_signatures_reversed_order(self) -> None:
         # Test comparing objects with same signatures but different order.
 
         # Remove all signatures and create new ones.
-        md = Metadata.from_bytes(self.metadata["snapshot"])
+        md: Metadata = self.objects["Metadata"]
         md.signatures = {"a": Signature("a", "a"), "b": Signature("b", "b")}
         md_2 = copy.deepcopy(md)
         # Reverse signatures order in md_2.
@@ -83,7 +121,7 @@ def test_md_eq_signatures_reversed_order(self) -> None:
 
     def test_md_eq_special_signatures_tests(self) -> None:
         # Test that metadata objects with different signatures are not equal.
-        md = Metadata.from_bytes(self.metadata["snapshot"])
+        md: Metadata = self.objects["Metadata"]
         md_2 = copy.deepcopy(md)
         md_2.signatures = {}
         self.assertNotEqual(md, md_2)
@@ -96,171 +134,6 @@ def test_md_eq_special_signatures_tests(self) -> None:
         md_2.signatures = ""  # type: ignore
         self.assertNotEqual(md, md_2)
 
-    def test_signed_eq_(self) -> None:
-        md = Metadata.from_bytes(self.metadata["snapshot"])
-        md_2: Metadata = self.copy_and_simple_assert(md)
-
-        # We don't need to make "signed" = None as that was done when testing
-        # metadata attribute modifications.
-        for attr, value in [("version", -1), ("spec_version", "0.0.0")]:
-            setattr(md_2.signed, attr, value)
-            self.assertNotEqual(md.signed, md_2.signed, f"Failed case: {attr}")
-            # Restore the old value of the attribute.
-            setattr(md_2.signed, attr, getattr(md.signed, attr))
-
-    def test_key_eq_(self) -> None:
-        key_dict = {
-            "keytype": "rsa",
-            "scheme": "rsassa-pss-sha256",
-            "keyval": {"public": "foo"},
-        }
-        key = Key.from_dict("12sa12", key_dict)
-        key_2: Key = self.copy_and_simple_assert(key)
-        for attr, value in [
-            ("keyid", "a"),
-            ("keytype", "foo"),
-            ("scheme", "b"),
-            ("keytype", "b"),
-        ]:
-            setattr(key_2, attr, value)
-            self.assertNotEqual(key, key_2, f"Failed case: {attr}")
-            # Restore the old value of the attribute.
-            setattr(key_2, attr, getattr(key, attr))
-
-    def test_role_eq_(self) -> None:
-        role_dict = {
-            "keyids": ["keyid1", "keyid2"],
-            "threshold": 3,
-        }
-        role = Role.from_dict(role_dict)
-        role_2: Role = self.copy_and_simple_assert(role)
-
-        for attr, value in [("keyids", []), ("threshold", 10)]:
-            setattr(role_2, attr, value)
-            self.assertNotEqual(role, role_2, f"Failed case: {attr}")
-            # Restore the old value of the attribute.
-            setattr(role_2, attr, getattr(role, attr))
-
-    def test_root_eq_(self) -> None:
-        md = Metadata.from_bytes(self.metadata["root"])
-        signed_copy: Root = self.copy_and_simple_assert(md.signed)
-
-        # Common attributes between Signed and Root doesn't need testing.
-        # Ignore mypy request for type annotations on attr and value
-        for attr, value in [  # type: ignore
-            ("consistent_snapshot", None),
-            ("keys", {}),
-            ("roles", {}),
-        ]:
-
-            setattr(signed_copy, attr, value)
-            self.assertNotEqual(md.signed, signed_copy, f"Failed case: {attr}")
-            # Restore the old value of the attribute.
-            setattr(signed_copy, attr, getattr(md.signed, attr))
-
-    def test_metafile_eq_(self) -> None:
-        metafile_dict = {
-            "version": 1,
-            "length": 12,
-            "hashes": {"sha256": "abc"},
-        }
-        metafile = MetaFile.from_dict(metafile_dict)
-        metafile_2: MetaFile = self.copy_and_simple_assert(metafile)
-
-        # Ignore mypy request for type annotations on attr and value
-        for attr, value in [  # type: ignore
-            ("version", None),
-            ("length", None),
-            ("hashes", {}),
-        ]:
-            setattr(metafile_2, attr, value)
-            self.assertNotEqual(metafile, metafile_2, f"Failed case: {attr}")
-            # Restore the old value of the attribute.
-            setattr(metafile_2, attr, getattr(metafile, attr))
-
-    def test_timestamp_eq_(self) -> None:
-        md = Metadata.from_bytes(self.metadata["timestamp"])
-        signed_copy: Timestamp = self.copy_and_simple_assert(md.signed)
-
-        # Common attributes between Signed and Timestamp doesn't need testing.
-        setattr(signed_copy, "snapshot_meta", None)
-        self.assertNotEqual(md.signed, signed_copy)
-
-    def test_snapshot_eq_(self) -> None:
-        md = Metadata.from_bytes(self.metadata["snapshot"])
-        signed_copy: Snapshot = self.copy_and_simple_assert(md.signed)
-
-        # Common attributes between Signed and Snapshot doesn't need testing.
-        setattr(signed_copy, "meta", None)
-        self.assertNotEqual(md.signed, signed_copy)
-
-    def test_delegated_role_eq_(self) -> None:
-        delegated_role_dict = {
-            "keyids": ["keyid"],
-            "name": "a",
-            "terminating": False,
-            "threshold": 1,
-            "paths": ["fn1", "fn2"],
-        }
-        delegated_role = DelegatedRole.from_dict(delegated_role_dict)
-        delegated_role_2: DelegatedRole = self.copy_and_simple_assert(
-            delegated_role
-        )
-
-        # Common attributes between DelegatedRole and Role doesn't need testing.
-        for attr, value in [
-            ("name", ""),
-            ("terminating", None),
-            ("paths", [""]),
-            ("path_hash_prefixes", [""]),
-        ]:
-            setattr(delegated_role_2, attr, value)
-            msg = f"Failed case: {attr}"
-            self.assertNotEqual(delegated_role, delegated_role_2, msg)
-            # Restore the old value of the attribute.
-            setattr(delegated_role_2, attr, getattr(delegated_role, attr))
-
-    def test_delegations_eq_(self) -> None:
-        delegations_dict = {
-            "keys": {
-                "keyid2": {
-                    "keytype": "ed25519",
-                    "scheme": "ed25519",
-                    "keyval": {"public": "bar"},
-                }
-            },
-            "roles": [
-                {
-                    "keyids": ["keyid2"],
-                    "name": "b",
-                    "terminating": True,
-                    "paths": ["fn2"],
-                    "threshold": 4,
-                }
-            ],
-        }
-        delegations = Delegations.from_dict(delegations_dict)
-        delegations_2: Delegations = self.copy_and_simple_assert(delegations)
-        # Ignore mypy request for type annotations on attr and value
-        for attr, value in [("keys", {}), ("roles", {})]:  # type: ignore
-            setattr(delegations_2, attr, value)
-            msg = f"Failed case: {attr}"
-            self.assertNotEqual(delegations, delegations_2, msg)
-            # Restore the old value of the attribute.
-            setattr(delegations_2, attr, getattr(delegations, attr))
-
-    def test_targetfile_eq_(self) -> None:
-        targetfile_dict = {
-            "length": 12,
-            "hashes": {"sha256": "abc"},
-        }
-        targetfile = TargetFile.from_dict(targetfile_dict, "file1.txt")
-        targetfile_2: TargetFile = self.copy_and_simple_assert(targetfile)
-
-        # Common attr between TargetFile and MetaFile doesn't need testing.
-        setattr(targetfile_2, "path", "")
-        self.assertNotEqual(targetfile, targetfile_2)
-
     def test_delegations_eq_roles_reversed_order(self) -> None:
         # Test comparing objects with same delegated roles but different order.
         role_one_dict = {
@@ -303,18 +176,6 @@ def test_delegations_eq_roles_reversed_order(self) -> None:
 
         self.assertEqual(delegations, delegations_2)
 
-    def test_targets_eq_(self) -> None:
-        md = Metadata.from_bytes(self.metadata["targets"])
-        signed_copy: Targets = self.copy_and_simple_assert(md.signed)
-
-        # Common attributes between Targets and Signed doesn't need testing.
-        # Ignore mypy request for type annotations on attr and value
-        for attr, value in [("targets", {}), ("delegations", [])]:  # type: ignore
-            setattr(signed_copy, attr, value)
-            self.assertNotEqual(md.signed, signed_copy, f"Failed case: {attr}")
-            # Restore the old value of the attribute.
-            setattr(signed_copy, attr, getattr(md.signed, attr))
-
 
 # Run unit test.
 if __name__ == "__main__":