diff --git a/tests/backends/test_memcached.py b/tests/backends/test_memcached.py
index 01d2f5b..317a5e4 100644
--- a/tests/backends/test_memcached.py
+++ b/tests/backends/test_memcached.py
@@ -322,13 +322,21 @@ async def test_memcached_keeps_raising_after_a_connection_failure(call) -> None:
 
 
 @pytest.mark.asyncio
-async def test_memcached_tries_a_failed_server_again_after_the_dead_timeout() -> None:
-    """A failed server is not skipped for pymemcache's default 60 seconds (#197)."""
+async def test_memcached_tries_a_failed_server_again_after_the_dead_timeout(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A failed server is not skipped for pymemcache's default 60 seconds (#197).
+
+    The backend hands `_DEAD_TIMEOUT` to pymemcache, which times it with the
+    real clock, so the test shortens it rather than wait the documented second.
+    """
+    assert _DEAD_TIMEOUT == 1  # the delay BACKENDS.md documents
+    monkeypatch.setattr("fastapi_cachex.backends.memcached._DEAD_TIMEOUT", 0.05)
     backend = _unreachable_backend()
     with pytest.raises(ConnectionRefusedError):
         await backend.get("trip")
 
-    await asyncio.sleep(_DEAD_TIMEOUT + 0.1)
+    await asyncio.sleep(0.1)
 
     with pytest.raises(ConnectionRefusedError):
         await backend.get("k")
diff --git a/tests/backends/test_memory.py b/tests/backends/test_memory.py
index b4fc3d4..1b8070a 100644
--- a/tests/backends/test_memory.py
+++ b/tests/backends/test_memory.py
@@ -13,6 +13,15 @@
 from fastapi_cachex.types import COUNTER_FINGERPRINT
 from fastapi_cachex.types import CacheEntry
 from fastapi_cachex.types import counter_entry
+from tests.conftest import Clock
+
+
+async def _until(condition: Callable[[], bool]) -> None:
+    """Give the background sweeper up to a second of real time to act."""
+    for _ in range(100):
+        if condition():
+            return
+        await asyncio.sleep(0.01)
 
 
 @pytest_asyncio.fixture
@@ -96,7 +105,7 @@ async def test_memory_backend_clear(memory_backend: MemoryBackend):
 
 
 @pytest.mark.asyncio
-async def test_memory_backend_ttl_expiry(memory_backend: MemoryBackend):
+async def test_memory_backend_ttl_expiry(memory_backend: MemoryBackend, clock: Clock):
     key = "test_key"
     value = CacheEntry(
         fingerprint="test_etag",
@@ -106,14 +115,14 @@ async def test_memory_backend_ttl_expiry(memory_backend: MemoryBackend):
     ttl = 1
 
     await memory_backend.set(key, value, ttl)
-    await asyncio.sleep(2)  # Wait for the TTL to expire
+    clock.advance(1.5)
     retrieved_value = await memory_backend.get(key)
 
     assert retrieved_value is None
 
 
 @pytest.mark.asyncio
-async def test_memory_backend_cleanup(memory_backend: MemoryBackend):
+async def test_memory_backend_cleanup(memory_backend: MemoryBackend, clock: Clock):
     key1 = "test_key1"
     value1 = CacheEntry(
         fingerprint="test_etag1",
@@ -131,7 +140,7 @@ async def test_memory_backend_cleanup(memory_backend: MemoryBackend):
 
     await memory_backend.set(key1, value1, ttl1)
     await memory_backend.set(key2, value2, ttl2)
-    await asyncio.sleep(2)  # Wait for the TTL of key1 to expire
+    clock.advance(1.5)  # past key1's TTL, well within key2's
     await memory_backend.cleanup()
 
     retrieved_value1 = await memory_backend.get(key1)
@@ -262,7 +271,9 @@ def test_aclose_only_cancels_a_task_on_another_loop():
 
 
 @pytest.mark.asyncio
-async def test_memory_backend_cleanup_task_impl():
+async def test_memory_backend_cleanup_task_impl(
+    clock: Clock, monkeypatch: pytest.MonkeyPatch
+):
     """The sweeper itself has to drop expired entries.
 
     Reading the keys back through `get` proves nothing about the sweeper:
@@ -271,16 +282,18 @@ async def test_memory_backend_cleanup_task_impl():
     dictionary is inspected directly instead, and neither key is ever read.
     """
     backend = MemoryBackend(cleanup_interval=1)
+    # Sweep every 10 ms of real time; the entries' TTLs run on `clock`.
+    monkeypatch.setattr(backend, "cleanup_interval", 0.01)
     expiring = CacheEntry(fingerprint="test_etag1", content=b"test_value1")
     surviving = CacheEntry(fingerprint="test_etag2", content=b"test_value2")
 
     await backend.set("expiring", expiring, ttl=1)
     await backend.set("surviving", surviving, ttl=60)
+    clock.advance(1.5)
     backend.start_cleanup()
 
     try:
-        # One full interval plus the entry's own TTL.
-        await asyncio.sleep(2)
+        await _until(lambda: "expiring" not in backend.cache)
 
         assert "expiring" not in backend.cache
         assert backend.cache["surviving"].value == surviving
@@ -735,7 +748,9 @@ async def test_memory_delete_many_counts_only_existing_keys(
 
 
 @pytest.mark.asyncio
-async def test_write_only_use_starts_the_cleanup_task():
+async def test_write_only_use_starts_the_cleanup_task(
+    clock: Clock, monkeypatch: pytest.MonkeyPatch
+):
     """A backend that is only written to still needs its sweeper running.
 
     Only `get` used to start it, so a write-mostly caller — `StateManager`
@@ -743,12 +758,14 @@ async def test_write_only_use_starts_the_cleanup_task():
     expired entries with nothing to remove them.
     """
     backend = MemoryBackend(cleanup_interval=1)
+    monkeypatch.setattr(backend, "cleanup_interval", 0.01)
 
     await backend.set("gone", CacheEntry(fingerprint="e", content=b"v"), ttl=1)
     await backend.set("stays", CacheEntry(fingerprint="e", content=b"v"), ttl=60)
+    clock.advance(1.5)
 
     try:
-        await asyncio.sleep(2)
+        await _until(lambda: "gone" not in backend.cache)
 
         # Nothing here ever calls `get`, so only the sweeper can have removed
         # the expired key — a task that merely exists would leave it in place.
@@ -759,7 +776,7 @@ async def test_write_only_use_starts_the_cleanup_task():
 
 
 @pytest.mark.asyncio
-async def test_get_evicts_the_expired_entry_it_skips():
+async def test_get_evicts_the_expired_entry_it_skips(clock: Clock):
     """A miss on an expired key must also free the memory it was holding.
 
     Asserting that `get` returns `None` says nothing about this: it returns
@@ -771,7 +788,7 @@ async def test_get_evicts_the_expired_entry_it_skips():
     await backend.set("k", CacheEntry(fingerprint="e", content=b"v"), ttl=1)
 
     try:
-        await asyncio.sleep(1.05)
+        clock.advance(1.05)
 
         assert await backend.get("k") is None
         assert "k" not in backend.cache
diff --git a/tests/conftest.py b/tests/conftest.py
index df00e67..f31bcc1 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,10 +1,22 @@
+import asyncio
+import time
+from datetime import datetime
+from datetime import tzinfo
+from types import SimpleNamespace
+
 import pytest
 import pytest_asyncio
 
+from fastapi_cachex.backends import memory
+from fastapi_cachex.backends.base import BaseCacheBackend
 from fastapi_cachex.backends.memory import MemoryBackend
 from fastapi_cachex.manager_proxy import CacheManagerProxy
 from fastapi_cachex.proxy import BackendProxy
+from fastapi_cachex.session import manager as session_manager
+from fastapi_cachex.session import models as session_models
 from fastapi_cachex.session.proxy import SessionManagerProxy
+from fastapi_cachex.state import manager as state_manager
+from fastapi_cachex.state import models as state_models
 from fastapi_cachex.state.proxy import StateManagerProxy
 
 # Every proxy is a process-wide singleton, so whatever one test installs is
@@ -43,3 +55,46 @@ def reset_proxy_singletons():
     yield
     for proxy in _PROXIES:
         proxy.set(None)
+
+
+class Clock:
+    """The wall clock the library reads, moved by hand instead of by sleeping."""
+
+    def __init__(self) -> None:
+        self.now = time.time()
+
+    def time(self) -> float:
+        return self.now
+
+    def advance(self, seconds: float) -> None:
+        self.now += seconds
+
+    async def wait(self, seconds: float, backend: BaseCacheBackend) -> None:
+        """Let `seconds` pass as far as `backend` can tell.
+
+        A live server expires keys on its own clock, which this one cannot
+        move, so for anything but the memory backend the time really passes.
+        """
+        self.advance(seconds)
+        if not isinstance(backend, MemoryBackend):
+            await asyncio.sleep(seconds)
+
+
+@pytest.fixture
+def clock(monkeypatch: pytest.MonkeyPatch) -> Clock:
+    """Point every time read behind a TTL or expiry check at a `Clock`.
+
+    That is `time.time()` in the memory backend and `datetime.now()` in the
+    session and state modules. PyJWT and live servers keep real time.
+    """
+    clock = Clock()
+
+    class ClockDatetime(datetime):
+        @classmethod
+        def now(cls, tz: tzinfo | None = None) -> datetime:  # type: ignore[override]
+            return datetime.fromtimestamp(clock.now, tz)
+
+    monkeypatch.setattr(memory, "time", SimpleNamespace(time=clock.time))
+    for module in (session_manager, session_models, state_manager, state_models):
+        monkeypatch.setattr(module, "datetime", ClockDatetime)
+    return clock
diff --git a/tests/session/test_jwt.py b/tests/session/test_jwt.py
index c33a31b..70dc811 100644
--- a/tests/session/test_jwt.py
+++ b/tests/session/test_jwt.py
@@ -5,7 +5,7 @@
 
 from __future__ import annotations
 
-import asyncio
+from typing import TYPE_CHECKING
 
 import pytest
 
@@ -15,6 +15,9 @@
 from fastapi_cachex.session.manager import SessionManager
 from fastapi_cachex.session.models import SessionUser
 
+if TYPE_CHECKING:
+    from tests.conftest import Clock
+
 jwt = pytest.importorskip("jwt")
 
 
@@ -79,13 +82,17 @@ async def test_jwt_wrong_audience_rejected() -> None:
 
 
 @pytest.mark.asyncio
-async def test_jwt_expiration_enforced() -> None:
+async def test_jwt_expiration_enforced(clock: Clock) -> None:
     backend = MemoryBackend()
     config = SessionConfig(secret_key="a" * 32, token_format="jwt", session_ttl=1)
     manager = SessionManager(backend, config)
 
+    # PyJWT checks `exp` against the real time, which `clock` cannot move, so
+    # the session is created in the past instead: its `exp` has already gone
+    # by. The backend entry and the session itself go by `clock` and are still
+    # current, so only the token check can reject it.
+    clock.advance(-5)
     _session, token = await manager.create_session(user=SessionUser(user_id="u1"))
-    await asyncio.sleep(1.2)
 
     # JWT should be expired before reaching session checks
     with pytest.raises(SessionTokenError):
diff --git a/tests/session/test_manager.py b/tests/session/test_manager.py
index bd5706a..39218c0 100644
--- a/tests/session/test_manager.py
+++ b/tests/session/test_manager.py
@@ -25,6 +25,7 @@
 from fastapi_cachex.session.models import SessionUser
 from fastapi_cachex.types import CacheEntry
 from fastapi_cachex.types import CacheItem
+from tests.conftest import Clock
 
 
 class DummySerializer:
@@ -223,10 +224,8 @@ async def test_user_agent_binding(backend: MemoryBackend) -> None:
 
 
 @pytest.mark.asyncio
-async def test_sliding_expiration(backend: MemoryBackend) -> None:
+async def test_sliding_expiration(backend: MemoryBackend, clock: Clock) -> None:
     """Test sliding expiration."""
-    import asyncio
-
     config = SessionConfig(
         secret_key="a" * 32,
         session_ttl=3600,
@@ -240,8 +239,7 @@ async def test_sliding_expiration(backend: MemoryBackend) -> None:
 
     original_expiry = session.expires_at
 
-    # Sleep briefly to ensure time passes
-    await asyncio.sleep(0.01)
+    clock.advance(1)
 
     # Set expiry to be past the threshold (only 1000 seconds left vs 3600 TTL)
     session.expires_at = datetime.now(timezone.utc) + timedelta(seconds=1000)
diff --git a/tests/session/test_models.py b/tests/session/test_models.py
index 646b5df..f043d2c 100644
--- a/tests/session/test_models.py
+++ b/tests/session/test_models.py
@@ -11,6 +11,7 @@
 from fastapi_cachex.session.models import SessionToken
 from fastapi_cachex.session.models import SessionUser
 from fastapi_cachex.session.token_serializers import SimpleTokenSerializer
+from tests.conftest import Clock
 
 
 def test_session_user_creation() -> None:
@@ -80,20 +81,17 @@ def test_session_is_expired() -> None:
     assert not session.is_expired()
 
 
-def test_session_renew() -> None:
+def test_session_renew(clock: Clock) -> None:
     """Test session renewal."""
-    import time
-
     session = Session()
     session.expires_at = datetime.now(timezone.utc) + timedelta(hours=1)
     old_expiry = session.expires_at
 
-    # Sleep briefly to ensure time difference
-    time.sleep(0.01)
+    clock.advance(1)
 
     session.renew(3600)  # Renew for 1 hour
 
-    assert session.expires_at >= old_expiry
+    assert session.expires_at > old_expiry
 
 
 def test_session_regenerate_id() -> None:
diff --git a/tests/state/test_manager.py b/tests/state/test_manager.py
index 64b41da..c104f39 100644
--- a/tests/state/test_manager.py
+++ b/tests/state/test_manager.py
@@ -22,6 +22,7 @@
 from fastapi_cachex.state.manager import StateManager
 from fastapi_cachex.state.models import StateData
 from fastapi_cachex.types import CacheEntry
+from tests.conftest import Clock
 from tests.live_servers import REDIS_HOST
 from tests.live_servers import REDIS_PORT
 from tests.live_servers import requires_redis
@@ -339,15 +340,14 @@ async def test_state_reuse_prevention(state_manager: StateManager) -> None:
 
 
 @pytest.mark.asyncio
-async def test_get_state_metadata_after_expire(state_manager: StateManager) -> None:
+async def test_get_state_metadata_after_expire(
+    state_manager: StateManager, clock: Clock
+) -> None:
     """Test retrieving metadata from an expired state."""
     # Create state with very short TTL
     state = await state_manager.create_state(ttl=1, metadata={"test": "data"})
 
-    # Wait for state to expire
-    import asyncio
-
-    await asyncio.sleep(1.1)
+    await clock.wait(1.1, state_manager.backend)
 
     # Try to retrieve metadata - should return None since it's expired
     retrieved = await state_manager.get_state_metadata(state)
diff --git a/tests/test_cache_manager.py b/tests/test_cache_manager.py
index 2f18aad..3952608 100644
--- a/tests/test_cache_manager.py
+++ b/tests/test_cache_manager.py
@@ -17,6 +17,7 @@
 from fastapi_cachex.manager_proxy import CacheManagerProxy
 from fastapi_cachex.proxy import BackendProxy
 from fastapi_cachex.types import CacheEntry
+from tests.conftest import Clock
 from tests.live_servers import REDIS_HOST
 from tests.live_servers import REDIS_PORT
 from tests.live_servers import requires_redis
@@ -216,14 +217,14 @@ async def load_user(user_id: int) -> dict[str, int]:
 
 @pytest.mark.asyncio
 async def test_get_or_set_honors_ttl_on_created_value(
-    cache_manager: CacheManager,
+    cache_manager: CacheManager, clock: Clock
 ) -> None:
     """get_or_set() applies the given ttl to a newly created value."""
     result = await cache_manager.get_or_set("key", lambda: "value", ttl=1)
     assert result == "value"
     assert await cache_manager.get("key") == "value"
 
-    await asyncio.sleep(1.2)
+    await clock.wait(1.2, cache_manager.backend)
 
     assert await cache_manager.get("key") is None
 
@@ -278,24 +279,28 @@ async def test_add_concurrent_callers_have_exactly_one_winner(
 
 
 @pytest.mark.asyncio
-async def test_add_ttl_expires_the_claim(cache_manager: CacheManager) -> None:
+async def test_add_ttl_expires_the_claim(
+    cache_manager: CacheManager, clock: Clock
+) -> None:
     """An explicit ttl applies, and once it lapses the key can be added again."""
     assert await cache_manager.add("event:1", "first", ttl=1) is True
     assert await cache_manager.add("event:1", "second", ttl=1) is False
 
-    await asyncio.sleep(1.2)
+    await clock.wait(1.2, cache_manager.backend)
 
     assert await cache_manager.add("event:1", "third") is True
     assert await cache_manager.get("event:1") == "third"
 
 
 @pytest.mark.asyncio
-async def test_add_uses_default_ttl(memory_backend: MemoryBackend) -> None:
+async def test_add_uses_default_ttl(
+    memory_backend: MemoryBackend, clock: Clock
+) -> None:
     """add() without an explicit ttl falls back to the manager's default_ttl."""
     manager = CacheManager(backend=memory_backend, default_ttl=1)
     assert await manager.add("event:1", "value") is True
 
-    await asyncio.sleep(1.2)
+    clock.advance(1.2)
 
     assert await manager.get("event:1") is None
 
@@ -360,19 +365,19 @@ async def test_has_missing_key_false(cache_manager: CacheManager) -> None:
 
 
 @pytest.mark.asyncio
-async def test_ttl_expiry(cache_manager: CacheManager) -> None:
+async def test_ttl_expiry(cache_manager: CacheManager, clock: Clock) -> None:
     """A value set with a short ttl expires and is no longer retrievable."""
     await cache_manager.set("key", "value", ttl=1)
     assert await cache_manager.get("key") == "value"
 
-    await asyncio.sleep(1.2)
+    await clock.wait(1.2, cache_manager.backend)
 
     assert await cache_manager.get("key") is None
 
 
 @pytest.mark.asyncio
 async def test_default_ttl_used_when_not_specified(
-    memory_backend: MemoryBackend,
+    memory_backend: MemoryBackend, clock: Clock
 ) -> None:
     """set() without an explicit ttl uses the manager's default_ttl."""
     BackendProxy.set(memory_backend)
@@ -381,21 +386,21 @@ async def test_default_ttl_used_when_not_specified(
     await manager.set("key", "value")
     assert await manager.get("key") == "value"
 
-    await asyncio.sleep(1.2)
+    clock.advance(1.2)
 
     assert await manager.get("key") is None
 
 
 @pytest.mark.asyncio
 async def test_explicit_ttl_overrides_default_ttl(
-    memory_backend: MemoryBackend,
+    memory_backend: MemoryBackend, clock: Clock
 ) -> None:
     """An explicit ttl on set() overrides a long default_ttl."""
     BackendProxy.set(memory_backend)
     manager = CacheManager(default_ttl=3600)
 
     await manager.set("key", "value", ttl=1)
-    await asyncio.sleep(1.2)
+    clock.advance(1.2)
 
     assert await manager.get("key") is None
 
diff --git a/tests/test_proxybackend.py b/tests/test_proxybackend.py
index 13e0056..35cdd70 100644
--- a/tests/test_proxybackend.py
+++ b/tests/test_proxybackend.py
@@ -1,4 +1,3 @@
-import asyncio
 import threading
 import time
 from collections.abc import Iterator
@@ -21,6 +20,7 @@
 from fastapi_cachex.session.proxy import SessionManagerProxy
 from fastapi_cachex.state.proxy import StateManagerProxy
 from fastapi_cachex.types import CacheEntry
+from tests.conftest import Clock
 
 app = FastAPI()
 client = TestClient(app)
@@ -84,7 +84,7 @@ async def test_endpoint():
 
 
 @pytest.mark.asyncio
-async def test_backend_cleanup():
+async def test_backend_cleanup(clock: Clock):
     # Run cleanup task in async environment
     memory_backend = MemoryBackend()
     BackendProxy.set(memory_backend)
@@ -101,8 +101,7 @@ async def test_backend_cleanup():
     assert cached_value is not None
     assert cached_value.content == b"test_value"
 
-    # Wait for data to expire (1 second + extra time)
-    await asyncio.sleep(1.1)
+    clock.advance(1.1)
 
     # Execute cleanup
     await memory_backend.cleanup()