diff --git a/changes.md b/changes.md
index 739473d6..1d4ff92c 100644
--- a/changes.md
+++ b/changes.md
@@ -27,6 +27,12 @@
   f-string upgrades, `object` base class removal) and removed it from the
   ruff exclude list. `tests/test_subject/` also removed from the ruff exclude
   list as it already passed all checks.
+- Testing: Fixed pyright (standard-mode) type errors in `tests/test_scheduler/`:
+  corrected `@classmethod` overrides of `VirtualTimeScheduler.add`,
+  fixed `[None]`-typed list variables, updated optional-import suppression
+  comments (`# type: ignore[import-untyped]`), narrowed callback parameter
+  types, and aligned `ScheduledItemTestScheduler` method signatures with the
+  `Scheduler` base class.
 - CI: Standardised `actions/setup-python` to `@v5` across all workflow jobs.
 
 ## 2.0.0-alpha
diff --git a/pyproject.toml b/pyproject.toml
index 91845f1c..ac6fc561 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -110,8 +110,8 @@ asyncio_mode = "strict"
 include = ["reactivex", "tests"]
 exclude = [
     # Stage 1 complete, Stage 2 partial (test_integration complete)
-    # test_subject and test_scheduler now pass ruff and pyright (run separately)
-    # keeping them excluded until strict-mode pyright issues are resolved
+    # test_subject and test_scheduler now pass ruff and pyright in standard mode
+    # keeping them excluded until type annotations are added to all callbacks (strict mode)
     "tests/test_subject",
     "tests/test_scheduler",
     "tests/test_observable",
diff --git a/tests/test_scheduler/test_catchscheduler.py b/tests/test_scheduler/test_catchscheduler.py
index b2023cb1..5d50064d 100644
--- a/tests/test_scheduler/test_catchscheduler.py
+++ b/tests/test_scheduler/test_catchscheduler.py
@@ -1,6 +1,7 @@
 import unittest
 from datetime import timedelta
 
+from reactivex import typing as rx_typing
 from reactivex.scheduler import CatchScheduler, VirtualTimeScheduler
 
 
@@ -13,8 +14,11 @@ def __init__(self, initial_clock=0.0):
         super().__init__(initial_clock)
         self.exc = None
 
-    def add(self, absolute, relative):
-        return absolute + relative
+    @classmethod
+    def add(
+        cls, absolute: rx_typing.AbsoluteTime, relative: rx_typing.RelativeTime
+    ) -> rx_typing.AbsoluteTime:
+        return absolute + relative  # type: ignore[operator]
 
     def _wrap(self, action):
         def _action(scheduler, state=None):
diff --git a/tests/test_scheduler/test_currentthreadscheduler.py b/tests/test_scheduler/test_currentthreadscheduler.py
index 6d8168eb..0421ac14 100644
--- a/tests/test_scheduler/test_currentthreadscheduler.py
+++ b/tests/test_scheduler/test_currentthreadscheduler.py
@@ -20,7 +20,7 @@ def test_currentthread_singleton(self):
         assert scheduler[1] is scheduler[2]
 
         gate = [threading.Semaphore(0), threading.Semaphore(0)]
-        scheduler = [None, None]
+        scheduler: list[CurrentThreadScheduler | None] = [None, None]
 
         def run(idx):
             scheduler[idx] = CurrentThreadScheduler.singleton()
diff --git a/tests/test_scheduler/test_eventloop/test_asyncioscheduler.py b/tests/test_scheduler/test_eventloop/test_asyncioscheduler.py
index bd49e29f..055b292c 100644
--- a/tests/test_scheduler/test_eventloop/test_asyncioscheduler.py
+++ b/tests/test_scheduler/test_eventloop/test_asyncioscheduler.py
@@ -6,6 +6,7 @@
 
 import pytest
 
+from reactivex import abc
 from reactivex.scheduler.eventloop import AsyncIOScheduler
 
 CI = os.getenv("CI") is not None
@@ -49,7 +50,7 @@ async def go():
                 scheduler = AsyncIOScheduler(loop)
                 ran = False
 
-                def action(scheduler: AsyncIOScheduler, state: Any):
+                def action(scheduler: abc.SchedulerBase, state: Any):
                     nonlocal ran
                     ran = True
 
diff --git a/tests/test_scheduler/test_eventloop/test_ioloopscheduler.py b/tests/test_scheduler/test_eventloop/test_ioloopscheduler.py
index 6f0f3ccb..68ac5470 100644
--- a/tests/test_scheduler/test_eventloop/test_ioloopscheduler.py
+++ b/tests/test_scheduler/test_eventloop/test_ioloopscheduler.py
@@ -7,7 +7,7 @@
 from reactivex.scheduler.eventloop import IOLoopScheduler
 
 tornado = pytest.importorskip("tornado")
-from tornado import ioloop  # noqa: E402
+from tornado import ioloop  # noqa: E402  # type: ignore[import-untyped]
 
 
 class TestIOLoopScheduler(unittest.TestCase):
diff --git a/tests/test_scheduler/test_eventloop/test_twistedscheduler.py b/tests/test_scheduler/test_eventloop/test_twistedscheduler.py
index 4c22a9c0..86d755d0 100644
--- a/tests/test_scheduler/test_eventloop/test_twistedscheduler.py
+++ b/tests/test_scheduler/test_eventloop/test_twistedscheduler.py
@@ -6,8 +6,11 @@
 from reactivex.scheduler.eventloop import TwistedScheduler
 
 twisted = pytest.importorskip("twisted")
-from twisted.internet import defer, reactor  # noqa: E402
-from twisted.trial import unittest  # noqa: E402
+from twisted.internet import (  # noqa: E402  # type: ignore[import-untyped]
+    defer,
+    reactor,
+)
+from twisted.trial import unittest  # noqa: E402  # type: ignore[import-untyped]
 
 
 class TestTwistedScheduler(unittest.TestCase):
diff --git a/tests/test_scheduler/test_eventloopscheduler.py b/tests/test_scheduler/test_eventloopscheduler.py
index 6ffa95a0..aafa8473 100644
--- a/tests/test_scheduler/test_eventloopscheduler.py
+++ b/tests/test_scheduler/test_eventloopscheduler.py
@@ -1,7 +1,7 @@
 import os
 import threading
 import unittest
-from datetime import timedelta
+from datetime import datetime, timedelta
 from time import sleep
 
 import pytest
@@ -132,7 +132,7 @@ def test_event_loop_schedule_action_relative_due(self):
         scheduler = EventLoopScheduler(exit_if_empty=True)
         gate = threading.Semaphore(0)
         starttime = default_now()
-        endtime = None
+        endtime: datetime | None = None
 
         def action(scheduler, state):
             nonlocal endtime
@@ -144,6 +144,7 @@ def action(scheduler, state):
         # There is no guarantee that the event-loop thread ends before the
         # test thread is re-scheduled, give it some time to always run.
         sleep(0.1)
+        assert endtime is not None
         diff = endtime - starttime
         assert diff > timedelta(milliseconds=180)
         assert scheduler._has_thread() is False
@@ -152,7 +153,7 @@ def test_event_loop_schedule_action_absolute_due(self):
         scheduler = EventLoopScheduler(exit_if_empty=True)
         gate = threading.Semaphore(0)
         starttime = default_now()
-        endtime = None
+        endtime: datetime | None = None
 
         def action(scheduler, state):
             nonlocal endtime
@@ -164,6 +165,7 @@ def action(scheduler, state):
         # There is no guarantee that the event-loop thread ends before the
         # test thread is re-scheduled, give it some time to always run.
         sleep(0.1)
+        assert endtime is not None
         diff = endtime - starttime
         assert diff < timedelta(milliseconds=180)
         assert scheduler._has_thread() is False
@@ -241,12 +243,12 @@ def test_eventloop_schedule_periodic_dispose_error(self):
 
         ran = False
 
-        def action(scheduler, state):
+        def action(state: None) -> None:
             nonlocal ran
             ran = True
 
         with pytest.raises(DisposedException):
-            scheduler.schedule_periodic(0.1, action)
+            scheduler.schedule_periodic(0.1, action)  # type: ignore[arg-type]
 
         assert ran is False
         assert scheduler._has_thread() is False
diff --git a/tests/test_scheduler/test_immediatescheduler.py b/tests/test_scheduler/test_immediatescheduler.py
index ad58cf69..9d72af9e 100644
--- a/tests/test_scheduler/test_immediatescheduler.py
+++ b/tests/test_scheduler/test_immediatescheduler.py
@@ -21,7 +21,7 @@ def test_immediate_singleton(self):
         assert scheduler[0] is scheduler[1]
 
         gate = [threading.Semaphore(0), threading.Semaphore(0)]
-        scheduler = [None, None]
+        scheduler: list[ImmediateScheduler | None] = [None, None]
 
         def run(idx):
             scheduler[idx] = ImmediateScheduler()
diff --git a/tests/test_scheduler/test_mainloop/test_gtkscheduler.py b/tests/test_scheduler/test_mainloop/test_gtkscheduler.py
index 50b087a6..d37ce995 100644
--- a/tests/test_scheduler/test_mainloop/test_gtkscheduler.py
+++ b/tests/test_scheduler/test_mainloop/test_gtkscheduler.py
@@ -10,7 +10,7 @@
 from reactivex.scheduler.mainloop import GtkScheduler
 
 gi = pytest.importorskip("gi")
-from gi.repository import GLib, Gtk  # noqa: E402, I001
+from gi.repository import GLib, Gtk  # noqa: E402, I001  # type: ignore[import-untyped]
 
 
 gi.require_version("Gtk", "3.0")
diff --git a/tests/test_scheduler/test_newthreadscheduler.py b/tests/test_scheduler/test_newthreadscheduler.py
index 049606e4..033e542f 100644
--- a/tests/test_scheduler/test_newthreadscheduler.py
+++ b/tests/test_scheduler/test_newthreadscheduler.py
@@ -75,13 +75,14 @@ def test_new_thread_schedule_periodic(self):
         period = 0.05
         counter = 3
 
-        def action(state: int):
+        def action(state: int | None) -> int | None:
             nonlocal counter
             if state:
                 counter -= 1
                 return state - 1
             if counter == 0:
                 gate.release()
+            return None
 
         scheduler.schedule_periodic(period, action, counter)
         gate.acquire()
@@ -92,11 +93,12 @@ def test_new_thread_schedule_periodic_cancel(self):
         period = 0.1
         counter = 4
 
-        def action(state: int):
+        def action(state: int | None) -> int | None:
             nonlocal counter
             if state:
                 counter -= 1
                 return state - 1
+            return None
 
         disp = scheduler.schedule_periodic(period, action, counter)
         sleep(0.4)
diff --git a/tests/test_scheduler/test_scheduleditem.py b/tests/test_scheduler/test_scheduleditem.py
index db18dd6d..28dfef95 100644
--- a/tests/test_scheduler/test_scheduleditem.py
+++ b/tests/test_scheduler/test_scheduleditem.py
@@ -1,6 +1,9 @@
 import unittest
 from datetime import timedelta
+from typing import Any
 
+from reactivex import abc
+from reactivex import typing as rx_typing
 from reactivex.disposable import Disposable
 from reactivex.internal.basic import default_now
 from reactivex.scheduler.scheduleditem import ScheduledItem
@@ -10,24 +13,42 @@
 class ScheduledItemTestScheduler(Scheduler):
     def __init__(self):
         super()
-        self.action = None
-        self.state = None
-        self.disposable = None
-
-    def invoke_action(self, action, state):
+        self.action: Any = None
+        self.state: Any = None
+        self.disposable: abc.DisposableBase | None = None
+
+    def invoke_action(
+        self,
+        action: abc.ScheduledAction[Any],
+        state: Any = None,
+    ) -> abc.DisposableBase:
         self.action = action
         self.state = state
         self.disposable = super().invoke_action(action, state)
         return self.disposable
 
-    def schedule(self, action, state):
-        pass
-
-    def schedule_relative(self, duetime, action, state):
-        pass
-
-    def schedule_absolute(self, duetime, action, state):
-        pass
+    def schedule(
+        self,
+        action: abc.ScheduledAction[Any],
+        state: Any = None,
+    ) -> abc.DisposableBase:
+        return Disposable()
+
+    def schedule_relative(
+        self,
+        duetime: rx_typing.RelativeTime,
+        action: abc.ScheduledAction[Any],
+        state: Any = None,
+    ) -> abc.DisposableBase:
+        return Disposable()
+
+    def schedule_absolute(
+        self,
+        duetime: rx_typing.AbsoluteTime,
+        action: abc.ScheduledAction[Any],
+        state: Any = None,
+    ) -> abc.DisposableBase:
+        return Disposable()
 
 
 class TestScheduledItem(unittest.TestCase):
diff --git a/tests/test_scheduler/test_timeoutscheduler.py b/tests/test_scheduler/test_timeoutscheduler.py
index 2a9e119a..516246f6 100644
--- a/tests/test_scheduler/test_timeoutscheduler.py
+++ b/tests/test_scheduler/test_timeoutscheduler.py
@@ -18,7 +18,7 @@ def test_timeout_singleton(self):
         assert scheduler[0] is scheduler[1]
 
         gate = [threading.Semaphore(0), threading.Semaphore(0)]
-        scheduler = [None, None]
+        scheduler: list[TimeoutScheduler | None] = [None, None]
 
         def run(idx):
             scheduler[idx] = TimeoutScheduler()
diff --git a/tests/test_scheduler/test_virtualtimescheduler.py b/tests/test_scheduler/test_virtualtimescheduler.py
index a1a03546..be606b5e 100644
--- a/tests/test_scheduler/test_virtualtimescheduler.py
+++ b/tests/test_scheduler/test_virtualtimescheduler.py
@@ -2,14 +2,18 @@
 
 import pytest
 
+from reactivex import typing as rx_typing
 from reactivex.internal import ArgumentOutOfRangeException
 from reactivex.internal.constants import DELTA_ZERO, UTC_ZERO
 from reactivex.scheduler import VirtualTimeScheduler
 
 
 class VirtualSchedulerTestScheduler(VirtualTimeScheduler):
-    def add(self, absolute, relative):
-        return absolute + relative
+    @classmethod
+    def add(
+        cls, absolute: rx_typing.AbsoluteTime, relative: rx_typing.RelativeTime
+    ) -> rx_typing.AbsoluteTime:
+        return absolute + relative  # type: ignore[operator]
 
 
 class TestVirtualTimeScheduler(unittest.TestCase):
@@ -24,7 +28,7 @@ def test_virtual_now_float(self):
         assert scheduler.now == UTC_ZERO
 
     def test_virtual_now_timedelta(self):
-        scheduler = VirtualSchedulerTestScheduler(DELTA_ZERO)
+        scheduler = VirtualSchedulerTestScheduler(DELTA_ZERO)  # type: ignore[arg-type]
         assert scheduler.clock == DELTA_ZERO
         assert scheduler.now == UTC_ZERO
 
@@ -69,4 +73,4 @@ def test_virtual_schedule_advance_clock_error(self):
         scheduler = VirtualSchedulerTestScheduler()
 
         with pytest.raises(ArgumentOutOfRangeException):
-            scheduler.advance_to(scheduler._clock - 1)
+            scheduler.advance_to(scheduler._clock - 1)  # type: ignore[operator]