diff --git a/src/tests/helpers.py b/src/tests/helpers.py
index 22c55cf..b6d61ec 100644
--- a/src/tests/helpers.py
+++ b/src/tests/helpers.py
@@ -30,3 +30,228 @@ def create_vault(
     enc_mgr = EncryptionManager(index_key, dir_path)
     vault = Vault(enc_mgr, dir_path)
     return vault, enc_mgr
+
+
+import uuid
+import asyncio
+import pytest
+
+from nostr.backup_models import (
+    KIND_MANIFEST,
+    KIND_SNAPSHOT_CHUNK,
+    KIND_DELTA,
+)
+
+
+class DummyEvent:
+    def __init__(self, kind: int, content: str, tags=None, event_id: str | None = None):
+        self.kind = kind
+        self._content = content
+        self.tags = tags or []
+        self.id = event_id or f"evt-{uuid.uuid4().hex}"
+
+    def content(self):
+        return self._content
+
+
+class DummyUnsignedEvent:
+    def __init__(self, kind: int, content: str, tags: list[str]):
+        self.kind = kind
+        self.content = content
+        self.tags = tags
+
+    def sign_with_keys(self, _keys):
+        return DummyEvent(self.kind, self.content, self.tags)
+
+
+class DummyBuilder:
+    def __init__(self, kind=None, content=""):
+        if hasattr(kind, "as_u16"):
+            self.kind = kind.as_u16()
+        elif hasattr(kind, "value"):
+            self.kind = kind.value
+        else:
+            self.kind = int(kind)
+        self.content = content
+        self._tags: list[str] = []
+
+    def tags(self, tags):
+        # store raw tag values
+        self._tags.extend(tags)
+        return self
+
+    def build(self, _pk):
+        return DummyUnsignedEvent(self.kind, self.content, self._tags)
+
+
+class DummyTag:
+    @staticmethod
+    def identifier(value):
+        return value
+
+    @staticmethod
+    def event(value):
+        return value
+
+    @staticmethod
+    def alt(value):
+        return value
+
+    @staticmethod
+    def expiration(value):
+        return value
+
+
+class DummyFilter:
+    def __init__(self):
+        self.kind_val: int | None = None
+        self.ids: list[str] = []
+        self.limit_val: int | None = None
+        self.since_val: int | None = None
+
+    def author(self, _pk):
+        return self
+
+    def kind(self, kind):
+        if hasattr(kind, "as_u16"):
+            self.kind_val = kind.as_u16()
+        elif hasattr(kind, "value"):
+            self.kind_val = kind.value
+        else:
+            self.kind_val = int(kind)
+        return self
+
+    def identifier(self, ident: str):
+        self.ids.append(ident)
+        return self
+
+    def limit(self, val: int):
+        self.limit_val = val
+        return self
+
+    def since(self, ts):
+        self.since_val = getattr(ts, "secs", ts)
+        return self
+
+
+class DummyTimestamp:
+    def __init__(self, secs: int):
+        self.secs = secs
+
+    @staticmethod
+    def from_secs(secs: int) -> "DummyTimestamp":
+        return DummyTimestamp(secs)
+
+
+class DummyEventId:
+    def __init__(self, val: str):
+        self.val = val
+
+    def to_hex(self) -> str:
+        return self.val
+
+    @staticmethod
+    def parse(val: str) -> str:
+        return val
+
+
+class DummySendResult:
+    def __init__(self, event_id: str):
+        self.id = DummyEventId(event_id)
+
+
+class DummyRelayClient:
+    def __init__(self):
+        self.counter = 0
+        self.manifests: list[DummyEvent] = []
+        self.chunks: dict[str, DummyEvent] = {}
+        self.deltas: list[DummyEvent] = []
+
+    async def add_relays(self, _relays):
+        pass
+
+    async def add_relay(self, _relay):
+        pass
+
+    async def connect(self):
+        pass
+
+    async def disconnect(self):
+        pass
+
+    async def send_event(self, event):
+        self.counter += 1
+        eid = str(self.counter)
+        if isinstance(event, DummyEvent):
+            event.id = eid
+        if event.kind == KIND_MANIFEST:
+            self.manifests.append(event)
+        elif event.kind == KIND_SNAPSHOT_CHUNK:
+            ident = event.tags[0] if event.tags else str(self.counter)
+            self.chunks[ident] = event
+        elif event.kind == KIND_DELTA:
+            self.deltas.append(event)
+        return DummySendResult(eid)
+
+    async def fetch_events(self, f, _timeout):
+        kind = getattr(f, "kind_val", None)
+        limit = getattr(f, "limit_val", None)
+        identifier = f.ids[0] if getattr(f, "ids", None) else None
+        since = getattr(f, "since_val", None)
+        events: list[DummyEvent] = []
+        if kind == KIND_MANIFEST:
+            events = list(reversed(self.manifests))
+        elif kind == KIND_SNAPSHOT_CHUNK and identifier is not None:
+            if identifier in self.chunks:
+                events = [self.chunks[identifier]]
+        elif kind == KIND_DELTA:
+            events = [d for d in self.deltas if since is None or int(d.id) > since]
+        if limit is not None:
+            events = events[:limit]
+
+        class Result:
+            def __init__(self, evs):
+                self._evs = evs
+
+            def to_vec(self):
+                return self._evs
+
+        return Result(events)
+
+
+@pytest.fixture
+def dummy_nostr_client(tmp_path, monkeypatch):
+    """Return a NostrClient wired to a DummyRelayClient."""
+    from cryptography.fernet import Fernet
+    from nostr.client import NostrClient
+
+    relay = DummyRelayClient()
+    monkeypatch.setattr("nostr.client.Client", lambda signer: relay)
+    monkeypatch.setattr("nostr.client.EventBuilder", DummyBuilder)
+    monkeypatch.setattr("nostr.client.Filter", DummyFilter)
+    monkeypatch.setattr("nostr.client.Tag", DummyTag)
+    monkeypatch.setattr("nostr.client.Timestamp", DummyTimestamp)
+    monkeypatch.setattr("nostr.client.EventId", DummyEventId)
+    from nostr.backup_models import KIND_DELTA as KD
+
+    monkeypatch.setattr("nostr.client.KIND_DELTA", KD, raising=False)
+    monkeypatch.setattr(NostrClient, "initialize_client_pool", lambda self: None)
+
+    enc_mgr = EncryptionManager(Fernet.generate_key(), tmp_path)
+
+    class DummyKeys:
+        def private_key_hex(self):
+            return "1" * 64
+
+        def public_key_hex(self):
+            return "2" * 64
+
+    class DummyKeyManager:
+        def __init__(self, *a, **k):
+            self.keys = DummyKeys()
+
+    with pytest.MonkeyPatch().context() as mp:
+        mp.setattr("nostr.client.KeyManager", DummyKeyManager)
+        mp.setattr(enc_mgr, "decrypt_parent_seed", lambda: TEST_SEED)
+        client = NostrClient(enc_mgr, "fp")
+    return client, relay
diff --git a/src/tests/test_nostr_dummy_client.py b/src/tests/test_nostr_dummy_client.py
new file mode 100644
index 0000000..cd1ab1a
--- /dev/null
+++ b/src/tests/test_nostr_dummy_client.py
@@ -0,0 +1,50 @@
+import asyncio
+import gzip
+import math
+
+from helpers import create_vault, dummy_nostr_client
+from password_manager.entry_management import EntryManager
+from nostr.client import prepare_snapshot
+
+
+def test_manifest_generation(tmp_path):
+    vault, enc_mgr = create_vault(tmp_path)
+    entry_mgr = EntryManager(vault, tmp_path)
+    entry_mgr.add_entry("example.com", 12)
+    entry_mgr.add_entry("test.com", 12)
+    encrypted = vault.get_encrypted_index()
+    assert encrypted
+    manifest, chunks = prepare_snapshot(encrypted, 100)
+    compressed = gzip.compress(encrypted)
+    expected = math.ceil(len(compressed) / 100)
+    assert len(chunks) == expected
+    assert len(manifest.chunks) == expected
+    for meta in manifest.chunks:
+        assert meta.id
+        assert meta.hash
+
+
+def test_retrieve_multi_chunk_snapshot(dummy_nostr_client):
+    import os
+
+    client, relay = dummy_nostr_client
+    data = os.urandom(120000)
+    manifest = asyncio.run(client.publish_snapshot(data, limit=50000))
+    assert len(manifest.chunks) > 1
+    fetched_manifest, chunk_bytes = asyncio.run(client.fetch_latest_snapshot())
+    assert len(chunk_bytes) == len(manifest.chunks)
+    joined = b"".join(chunk_bytes)
+    assert gzip.decompress(joined) == data
+
+
+def test_publish_and_fetch_deltas(dummy_nostr_client):
+    client, relay = dummy_nostr_client
+    base = b"base"
+    manifest = asyncio.run(client.publish_snapshot(base))
+    manifest_id = relay.manifests[-1].id
+    d1 = b"d1"
+    d2 = b"d2"
+    asyncio.run(client.publish_delta(d1, manifest_id))
+    asyncio.run(client.publish_delta(d2, manifest_id))
+    deltas = asyncio.run(client.fetch_deltas_since(0))
+    assert deltas == [d1, d2]