diff --git a/tests/repository_simulator.py b/tests/repository_simulator.py
index f5f4209bef..56bb9dafe0 100644
--- a/tests/repository_simulator.py
+++ b/tests/repository_simulator.py
@@ -249,8 +249,6 @@ def _fetch_metadata(
 
             if md is None:
                 raise FetcherHTTPError(f"Unknown role {role}", 404)
-            if version is not None and version != md.signed.version:
-                raise FetcherHTTPError(f"Unknown {role} version {version}", 404)
 
             md.signatures.clear()
             for signer in self.signers[role].values():
diff --git a/tests/test_updater_top_level_update.py b/tests/test_updater_top_level_update.py
new file mode 100644
index 0000000000..2dbb973979
--- /dev/null
+++ b/tests/test_updater_top_level_update.py
@@ -0,0 +1,439 @@
+#!/usr/bin/env python
+
+# Copyright 2021, New York University and the TUF contributors
+# SPDX-License-Identifier: MIT OR Apache-2.0
+
+"""Test ngclient Updater top-level metadata update workflow"""
+
+import os
+import sys
+import tempfile
+import unittest
+from datetime import datetime, timedelta
+from typing import Iterable, Optional
+
+from tests import utils
+from tests.repository_simulator import RepositorySimulator
+from tuf.api.metadata import TOP_LEVEL_ROLE_NAMES, Metadata
+from tuf.exceptions import (
+    BadVersionNumberError,
+    ExpiredMetadataError,
+    ReplayedMetadataError,
+    RepositoryError,
+    UnsignedMetadataError,
+)
+from tuf.ngclient import Updater
+
+
+class TestRefresh(unittest.TestCase):
+    """Test update of top-level metadata following
+    'Detailed client workflow' in the specification."""
+
+    past_datetime = datetime.utcnow().replace(microsecond=0) - timedelta(days=5)
+
+    def setUp(self) -> None:
+        self.temp_dir = tempfile.TemporaryDirectory()
+        self.metadata_dir = os.path.join(self.temp_dir.name, "metadata")
+        self.targets_dir = os.path.join(self.temp_dir.name, "targets")
+        os.mkdir(self.metadata_dir)
+        os.mkdir(self.targets_dir)
+
+        self.sim = RepositorySimulator()
+
+        with open(os.path.join(self.metadata_dir, "root.json"), "bw") as f:
+            root = self.sim.download_bytes(
+                "https://example.com/metadata/1.root.json", 100000
+            )
+            f.write(root)
+
+    def tearDown(self) -> None:
+        self.temp_dir.cleanup()
+
+    def _run_refresh(self) -> Updater:
+        """Create a new Updater instance and refresh"""
+        updater = Updater(
+            self.metadata_dir,
+            "https://example.com/metadata/",
+            self.targets_dir,
+            "https://example.com/targets/",
+            self.sim,
+        )
+        updater.refresh()
+        return updater
+
+    def _init_updater(self) -> Updater:
+        """Create a new Updater instance"""
+        return Updater(
+            self.metadata_dir,
+            "https://example.com/metadata/",
+            self.targets_dir,
+            "https://example.com/targets/",
+            self.sim,
+        )
+
+    def _assert_files_exist(self, roles: Iterable[str]) -> None:
+        """Assert that local metadata files exist for 'roles'"""
+        expected_files = sorted([f"{role}.json" for role in roles])
+        local_metadata_files = sorted(os.listdir(self.metadata_dir))
+        self.assertListEqual(local_metadata_files, expected_files)
+
+    def _assert_content_equals(
+        self, role: str, version: Optional[int] = None
+    ) -> None:
+        """Assert that local file content is the expected"""
+        expected_content = self.sim._fetch_metadata(role, version)
+        with open(os.path.join(self.metadata_dir, f"{role}.json"), "rb") as f:
+            self.assertEqual(f.read(), expected_content)
+
+    def _assert_version_equals(self, role: str, expected_version: int) -> None:
+        """Assert that local metadata version is the expected"""
+        md = Metadata.from_file(os.path.join(self.metadata_dir, f"{role}.json"))
+        self.assertEqual(md.signed.version, expected_version)
+
+    def test_first_time_refresh(self) -> None:
+        # Metadata dir contains only the mandatory initial root.json
+        self._assert_files_exist(["root"])
+
+        # Add one more root version to repository so that
+        # refresh() updates from local trusted root (v1) to
+        # remote root (v2)
+        self.sim.root.version += 1
+        self.sim.publish_root()
+
+        self._run_refresh()
+
+        self._assert_files_exist(TOP_LEVEL_ROLE_NAMES)
+        for role in TOP_LEVEL_ROLE_NAMES:
+            version = 2 if role == "root" else None
+            self._assert_content_equals(role, version)
+
+    def test_trusted_root_missing(self) -> None:
+        os.remove(os.path.join(self.metadata_dir, "root.json"))
+        with self.assertRaises(OSError):
+            self._run_refresh()
+
+        # Metadata dir is empty
+        self.assertFalse(os.listdir(self.metadata_dir))
+
+    def test_trusted_root_expired(self) -> None:
+        # Create an expired root version
+        self.sim.root.expires = self.past_datetime
+        self.sim.root.version += 1
+        self.sim.publish_root()
+
+        # Update to latest root which is expired but still
+        # saved as a local root.
+        updater = self._init_updater()
+        with self.assertRaises(ExpiredMetadataError):
+            updater.refresh()
+
+        self._assert_files_exist(["root"])
+        self._assert_content_equals("root", 2)
+
+        # Local root metadata can be loaded even if expired
+        updater = self._init_updater()
+
+        # Create a non-expired root version and refresh
+        self.sim.root.expires = self.sim.safe_expiry
+        self.sim.root.version += 1
+        self.sim.publish_root()
+        updater.refresh()
+
+        # Root is successfully updated to latest version
+        self._assert_files_exist(TOP_LEVEL_ROLE_NAMES)
+        self._assert_content_equals("root", 3)
+
+    def test_trusted_root_unsigned(self) -> None:
+        # Local trusted root is not signed
+        root_path = os.path.join(self.metadata_dir, "root.json")
+        md_root = Metadata.from_file(root_path)
+        md_root.signatures.clear()
+        md_root.to_file(root_path)
+
+        with self.assertRaises(UnsignedMetadataError):
+            self._run_refresh()
+
+        # The update failed, no changes in metadata
+        self._assert_files_exist(["root"])
+        md_root_after = Metadata.from_file(root_path)
+        self.assertEqual(md_root.to_bytes(), md_root_after.to_bytes())
+
+    def test_max_root_rotations(self) -> None:
+        # Root must stop looking for new versions after Y number of
+        # intermediate files were downloaded.
+        updater = self._init_updater()
+        updater.config.max_root_rotations = 3
+
+        # Create some number of roots greater than 'max_root_rotations'
+        while self.sim.root.version < updater.config.max_root_rotations + 3:
+            self.sim.root.version += 1
+            self.sim.publish_root()
+
+        md_root = Metadata.from_file(
+            os.path.join(self.metadata_dir, "root.json")
+        )
+        initial_root_version = md_root.signed.version
+
+        updater.refresh()
+
+        # Assert that root version was increased with no more
+        # than 'max_root_rotations'
+        self._assert_version_equals(
+            "root", initial_root_version + updater.config.max_root_rotations
+        )
+
+    def test_intermediate_root_incorrectly_signed(self) -> None:
+        # Check for an arbitrary software attack
+
+        # Intermediate root v2 is unsigned
+        self.sim.root.version += 1
+        root_signers = self.sim.signers["root"].copy()
+        self.sim.signers["root"].clear()
+        self.sim.publish_root()
+
+        # Final root v3 is correctly signed
+        self.sim.root.version += 1
+        self.sim.signers["root"] = root_signers
+        self.sim.publish_root()
+
+        # Incorrectly signed intermediate root is detected
+        with self.assertRaises(UnsignedMetadataError):
+            self._run_refresh()
+
+        # The update failed, latest root version is v1
+        self._assert_files_exist(["root"])
+        self._assert_content_equals("root", 1)
+
+    def test_intermediate_root_expired(self) -> None:
+        # The expiration of the new (intermediate) root metadata file
+        # does not matter yet
+
+        # Intermediate root v2 is expired
+        self.sim.root.expires = self.past_datetime
+        self.sim.root.version += 1
+        self.sim.publish_root()
+
+        # Final root v3 is up to date
+        self.sim.root.expires = self.sim.safe_expiry
+        self.sim.root.version += 1
+        self.sim.publish_root()
+
+        self._run_refresh()
+
+        # Successfully updated to root v3
+        self._assert_files_exist(TOP_LEVEL_ROLE_NAMES)
+        self._assert_content_equals("root", 3)
+
+    def test_final_root_incorrectly_signed(self) -> None:
+        # Check for an arbitrary software attack
+        self.sim.root.version += 1  # root v2
+        self.sim.signers["root"].clear()
+        self.sim.publish_root()
+
+        with self.assertRaises(UnsignedMetadataError):
+            self._run_refresh()
+
+        # The update failed, latest root version is v1
+        self._assert_files_exist(["root"])
+        self._assert_content_equals("root", 1)
+
+    def test_new_root_same_version(self) -> None:
+        # Check for a rollback_attack
+        # Repository serves a root file with the same version as previous
+        self.sim.publish_root()
+        with self.assertRaises(ReplayedMetadataError):
+            self._run_refresh()
+
+        # The update failed, latest root version is v1
+        self._assert_files_exist(["root"])
+        self._assert_content_equals("root", 1)
+
+    def test_new_root_nonconsecutive_version(self) -> None:
+        # Repository serves non-consecutive root version
+        self.sim.root.version += 2
+        self.sim.publish_root()
+        with self.assertRaises(ReplayedMetadataError):
+            self._run_refresh()
+
+        # The update failed, latest root version is v1
+        self._assert_files_exist(["root"])
+        self._assert_content_equals("root", 1)
+
+    def test_final_root_expired(self) -> None:
+        # Check for a freeze attack
+        # Final root is expired
+        self.sim.root.expires = self.past_datetime
+        self.sim.root.version += 1
+        self.sim.publish_root()
+
+        with self.assertRaises(ExpiredMetadataError):
+            self._run_refresh()
+
+        # The update failed but final root is persisted on the file system
+        self._assert_files_exist(["root"])
+        self._assert_content_equals("root", 2)
+
+    def test_new_timestamp_unsigned(self) -> None:
+        # Check for an arbitrary software attack
+        self.sim.signers["timestamp"].clear()
+        with self.assertRaises(UnsignedMetadataError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root"])
+
+    def test_new_timestamp_version_rollback(self) -> None:
+        # Check for a rollback attack
+        self.sim.timestamp.version = 2
+        self._run_refresh()
+
+        self.sim.timestamp.version = 1
+        with self.assertRaises(ReplayedMetadataError):
+            self._run_refresh()
+
+        self._assert_version_equals("timestamp", 2)
+
+    def test_new_timestamp_snapshot_rollback(self) -> None:
+        # Check for a rollback attack.
+        self.sim.snapshot.version = 2
+        self.sim.update_timestamp()  # timestamp v2
+        self._run_refresh()
+
+        # Snapshot meta version is smaller than previous
+        self.sim.timestamp.snapshot_meta.version = 1
+        self.sim.timestamp.version += 1  # timestamp v3
+
+        with self.assertRaises(ReplayedMetadataError):
+            self._run_refresh()
+
+        self._assert_version_equals("timestamp", 2)
+
+    def test_new_timestamp_expired(self) -> None:
+        # Check for a freeze attack
+        self.sim.timestamp.expires = self.past_datetime
+        self.sim.update_timestamp()
+
+        with self.assertRaises(ExpiredMetadataError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root"])
+
+    def test_new_snapshot_hash_mismatch(self) -> None:
+        # Check against timestamp role’s snapshot hash
+
+        # Update timestamp with snapshot's hashes
+        self.sim.compute_metafile_hashes_length = True
+        self.sim.update_timestamp()  # timestamp v2
+        self._run_refresh()
+
+        # Modify snapshot contents without updating
+        # timestamp's snapshot hash
+        self.sim.snapshot.expires += timedelta(days=1)
+        self.sim.snapshot.version += 1  # snapshot v2
+        self.sim.timestamp.snapshot_meta.version = self.sim.snapshot.version
+        self.sim.timestamp.version += 1  # timestamp v3
+
+        # Hash mismatch error
+        with self.assertRaises(RepositoryError):
+            self._run_refresh()
+
+        self._assert_version_equals("timestamp", 3)
+        self._assert_version_equals("snapshot", 1)
+
+    def test_new_snapshot_unsigned(self) -> None:
+        # Check for an arbitrary software attack
+        self.sim.signers["snapshot"].clear()
+        with self.assertRaises(UnsignedMetadataError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root", "timestamp"])
+
+    def test_new_snapshot_version_mismatch(self):
+        # Check against timestamp role’s snapshot version
+
+        # Increase snapshot version without updating timestamp
+        self.sim.snapshot.version += 1
+        with self.assertRaises(BadVersionNumberError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root", "timestamp"])
+
+    def test_new_snapshot_version_rollback(self) -> None:
+        # Check for a rollback attack
+        self.sim.snapshot.version = 2
+        self.sim.update_timestamp()
+        self._run_refresh()
+
+        self.sim.snapshot.version = 1
+        self.sim.update_timestamp()
+
+        with self.assertRaises(ReplayedMetadataError):
+            self._run_refresh()
+
+        self._assert_version_equals("snapshot", 2)
+
+    def test_new_snapshot_expired(self) -> None:
+        # Check for a freeze attack
+        self.sim.snapshot.expires = self.past_datetime
+        self.sim.update_snapshot()
+
+        with self.assertRaises(ExpiredMetadataError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root", "timestamp"])
+
+    def test_new_targets_hash_mismatch(self) -> None:
+        # Check against snapshot role’s targets hashes
+
+        # Update snapshot with target's hashes
+        self.sim.compute_metafile_hashes_length = True
+        self.sim.update_snapshot()
+        self._run_refresh()
+
+        # Modify targets contents without updating
+        # snapshot's targets hashes
+        self.sim.targets.version += 1
+        self.sim.snapshot.meta[
+            "targets.json"
+        ].version = self.sim.targets.version
+        self.sim.snapshot.version += 1
+        self.sim.update_timestamp()
+
+        with self.assertRaises(RepositoryError):
+            self._run_refresh()
+
+        self._assert_version_equals("snapshot", 3)
+        self._assert_version_equals("targets", 1)
+
+    def test_new_targets_unsigned(self) -> None:
+        # Check for an arbitrary software attack
+        self.sim.signers["targets"].clear()
+        with self.assertRaises(UnsignedMetadataError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root", "timestamp", "snapshot"])
+
+    def test_new_targets_version_mismatch(self):
+        # Check against snapshot role’s targets version
+
+        # Increase targets version without updating snapshot
+        self.sim.targets.version += 1
+        with self.assertRaises(BadVersionNumberError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root", "timestamp", "snapshot"])
+
+    def test_new_targets_expired(self) -> None:
+        # Check for a freeze attack.
+        self.sim.targets.expires = self.past_datetime
+        self.sim.update_snapshot()
+
+        with self.assertRaises(ExpiredMetadataError):
+            self._run_refresh()
+
+        self._assert_files_exist(["root", "timestamp", "snapshot"])
+
+
+if __name__ == "__main__":
+
+    utils.configure_test_logging(sys.argv)
+    unittest.main()