diff --git a/.coveragerc b/.coveragerc
index 4bbac7b27d..83a7cf0647 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -6,7 +6,7 @@ source=trio
 omit=
   setup.py
   */ipython_custom_exc.py
-# Omit the generated files in trio/_core starting with _public_
+# Omit the generated files in trio/_core starting with _generated_
   */trio/_core/_generated_*
 # The test suite spawns subprocesses to test some stuff, so make sure
 # this doesn't corrupt the coverage files
diff --git a/MANIFEST.in b/MANIFEST.in
index e2fd4c157f..8b92523fb7 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -2,6 +2,6 @@ include LICENSE LICENSE.MIT LICENSE.APACHE2
 include README.rst
 include CODE_OF_CONDUCT.md CONTRIBUTING.md
 include test-requirements.txt
-recursive-include trio/tests/test_ssl_certs *.pem
+recursive-include trio/_tests/test_ssl_certs *.pem
 recursive-include docs *
 prune docs/build
diff --git a/ci.sh b/ci.sh
index 2fc44c0b45..3cd78cfb18 100755
--- a/ci.sh
+++ b/ci.sh
@@ -81,7 +81,7 @@ else
         # when installing, and then running 'certmgr.msc' and exporting the
         # certificate. See:
         #    http://www.migee.com/2010/09/24/solution-for-unattendedsilent-installs-and-would-you-like-to-install-this-device-software/
-        certutil -addstore "TrustedPublisher" trio/tests/astrill-codesigning-cert.cer
+        certutil -addstore "TrustedPublisher" trio/_tests/astrill-codesigning-cert.cer
         # Double-slashes are how you tell windows-bash that you want a single
         # slash, and don't treat this as a unix-style filename that needs to
         # be replaced by a windows-style filename.
@@ -107,7 +107,7 @@ else
     # 'coverage xml' to generate the report that it uses, and that will only
     # apply the ignore patterns in the current directory's .coveragerc.
     cp ../.coveragerc .
-    if pytest -r a --junitxml=../test-results.xml --run-slow ${INSTALLDIR} --cov="$INSTALLDIR" --verbose; then
+    if pytest -r a -p trio._tests.pytest_plugin --junitxml=../test-results.xml --run-slow ${INSTALLDIR} --cov="$INSTALLDIR" --verbose; then
         PASSED=true
     else
         PASSED=false
diff --git a/trio/_core/tests/__init__.py b/trio/_core/_tests/__init__.py
similarity index 100%
rename from trio/_core/tests/__init__.py
rename to trio/_core/_tests/__init__.py
diff --git a/trio/_core/tests/test_asyncgen.py b/trio/_core/_tests/test_asyncgen.py
similarity index 100%
rename from trio/_core/tests/test_asyncgen.py
rename to trio/_core/_tests/test_asyncgen.py
diff --git a/trio/_core/tests/test_guest_mode.py b/trio/_core/_tests/test_guest_mode.py
similarity index 100%
rename from trio/_core/tests/test_guest_mode.py
rename to trio/_core/_tests/test_guest_mode.py
diff --git a/trio/_core/tests/test_instrumentation.py b/trio/_core/_tests/test_instrumentation.py
similarity index 100%
rename from trio/_core/tests/test_instrumentation.py
rename to trio/_core/_tests/test_instrumentation.py
diff --git a/trio/_core/tests/test_io.py b/trio/_core/_tests/test_io.py
similarity index 100%
rename from trio/_core/tests/test_io.py
rename to trio/_core/_tests/test_io.py
diff --git a/trio/_core/tests/test_ki.py b/trio/_core/_tests/test_ki.py
similarity index 100%
rename from trio/_core/tests/test_ki.py
rename to trio/_core/_tests/test_ki.py
diff --git a/trio/_core/tests/test_local.py b/trio/_core/_tests/test_local.py
similarity index 100%
rename from trio/_core/tests/test_local.py
rename to trio/_core/_tests/test_local.py
diff --git a/trio/_core/tests/test_mock_clock.py b/trio/_core/_tests/test_mock_clock.py
similarity index 100%
rename from trio/_core/tests/test_mock_clock.py
rename to trio/_core/_tests/test_mock_clock.py
diff --git a/trio/_core/tests/test_multierror.py b/trio/_core/_tests/test_multierror.py
similarity index 100%
rename from trio/_core/tests/test_multierror.py
rename to trio/_core/_tests/test_multierror.py
diff --git a/trio/_core/tests/test_multierror_scripts/__init__.py b/trio/_core/_tests/test_multierror_scripts/__init__.py
similarity index 100%
rename from trio/_core/tests/test_multierror_scripts/__init__.py
rename to trio/_core/_tests/test_multierror_scripts/__init__.py
diff --git a/trio/_core/tests/test_multierror_scripts/_common.py b/trio/_core/_tests/test_multierror_scripts/_common.py
similarity index 100%
rename from trio/_core/tests/test_multierror_scripts/_common.py
rename to trio/_core/_tests/test_multierror_scripts/_common.py
diff --git a/trio/_core/tests/test_multierror_scripts/apport_excepthook.py b/trio/_core/_tests/test_multierror_scripts/apport_excepthook.py
similarity index 100%
rename from trio/_core/tests/test_multierror_scripts/apport_excepthook.py
rename to trio/_core/_tests/test_multierror_scripts/apport_excepthook.py
diff --git a/trio/_core/tests/test_multierror_scripts/ipython_custom_exc.py b/trio/_core/_tests/test_multierror_scripts/ipython_custom_exc.py
similarity index 100%
rename from trio/_core/tests/test_multierror_scripts/ipython_custom_exc.py
rename to trio/_core/_tests/test_multierror_scripts/ipython_custom_exc.py
diff --git a/trio/_core/tests/test_multierror_scripts/simple_excepthook.py b/trio/_core/_tests/test_multierror_scripts/simple_excepthook.py
similarity index 100%
rename from trio/_core/tests/test_multierror_scripts/simple_excepthook.py
rename to trio/_core/_tests/test_multierror_scripts/simple_excepthook.py
diff --git a/trio/_core/tests/test_multierror_scripts/simple_excepthook_IPython.py b/trio/_core/_tests/test_multierror_scripts/simple_excepthook_IPython.py
similarity index 100%
rename from trio/_core/tests/test_multierror_scripts/simple_excepthook_IPython.py
rename to trio/_core/_tests/test_multierror_scripts/simple_excepthook_IPython.py
diff --git a/trio/_core/tests/test_parking_lot.py b/trio/_core/_tests/test_parking_lot.py
similarity index 100%
rename from trio/_core/tests/test_parking_lot.py
rename to trio/_core/_tests/test_parking_lot.py
diff --git a/trio/_core/tests/test_run.py b/trio/_core/_tests/test_run.py
similarity index 100%
rename from trio/_core/tests/test_run.py
rename to trio/_core/_tests/test_run.py
diff --git a/trio/_core/tests/test_thread_cache.py b/trio/_core/_tests/test_thread_cache.py
similarity index 100%
rename from trio/_core/tests/test_thread_cache.py
rename to trio/_core/_tests/test_thread_cache.py
diff --git a/trio/_core/tests/test_tutil.py b/trio/_core/_tests/test_tutil.py
similarity index 100%
rename from trio/_core/tests/test_tutil.py
rename to trio/_core/_tests/test_tutil.py
diff --git a/trio/_core/tests/test_unbounded_queue.py b/trio/_core/_tests/test_unbounded_queue.py
similarity index 100%
rename from trio/_core/tests/test_unbounded_queue.py
rename to trio/_core/_tests/test_unbounded_queue.py
diff --git a/trio/_core/tests/test_util.py b/trio/_core/_tests/test_util.py
similarity index 100%
rename from trio/_core/tests/test_util.py
rename to trio/_core/_tests/test_util.py
diff --git a/trio/_core/tests/test_windows.py b/trio/_core/_tests/test_windows.py
similarity index 100%
rename from trio/_core/tests/test_windows.py
rename to trio/_core/_tests/test_windows.py
diff --git a/trio/_core/tests/tutil.py b/trio/_core/_tests/tutil.py
similarity index 97%
rename from trio/_core/tests/tutil.py
rename to trio/_core/_tests/tutil.py
index 74760df38f..dc9a4f486d 100644
--- a/trio/_core/tests/tutil.py
+++ b/trio/_core/_tests/tutil.py
@@ -12,8 +12,8 @@
 
 import gc
 
-# See trio/tests/conftest.py for the other half of this
-from trio.tests.conftest import RUN_SLOW
+# See trio/_tests/conftest.py for the other half of this
+from trio._tests.pytest_plugin import RUN_SLOW
 
 slow = pytest.mark.skipif(not RUN_SLOW, reason="use --run-slow to run slow tests")
 
diff --git a/trio/_core/tests/conftest.py b/trio/_core/tests/conftest.py
deleted file mode 100644
index aca1f98a65..0000000000
--- a/trio/_core/tests/conftest.py
+++ /dev/null
@@ -1,25 +0,0 @@
-import pytest
-import inspect
-
-# XX this should move into a global something
-from ...testing import MockClock, trio_test
-
-
-@pytest.fixture
-def mock_clock():
-    return MockClock()
-
-
-@pytest.fixture
-def autojump_clock():
-    return MockClock(autojump_threshold=0)
-
-
-# FIXME: split off into a package (or just make part of Trio's public
-# interface?), with config file to enable? and I guess a mark option too; I
-# guess it's useful with the class- and file-level marking machinery (where
-# the raw @trio_test decorator isn't enough).
-@pytest.hookimpl(tryfirst=True)
-def pytest_pyfunc_call(pyfuncitem):
-    if inspect.iscoroutinefunction(pyfuncitem.obj):
-        pyfuncitem.obj = trio_test(pyfuncitem.obj)
diff --git a/trio/tests/__init__.py b/trio/_tests/__init__.py
similarity index 100%
rename from trio/tests/__init__.py
rename to trio/_tests/__init__.py
diff --git a/trio/tests/astrill-codesigning-cert.cer b/trio/_tests/astrill-codesigning-cert.cer
similarity index 100%
rename from trio/tests/astrill-codesigning-cert.cer
rename to trio/_tests/astrill-codesigning-cert.cer
diff --git a/trio/tests/module_with_deprecations.py b/trio/_tests/module_with_deprecations.py
similarity index 100%
rename from trio/tests/module_with_deprecations.py
rename to trio/_tests/module_with_deprecations.py
diff --git a/trio/tests/conftest.py b/trio/_tests/pytest_plugin.py
similarity index 80%
rename from trio/tests/conftest.py
rename to trio/_tests/pytest_plugin.py
index 772486e1eb..a893b466cb 100644
--- a/trio/tests/conftest.py
+++ b/trio/_tests/pytest_plugin.py
@@ -1,9 +1,3 @@
-# XX this does not belong here -- b/c it's here, these things only apply to
-# the tests in trio/_core/tests, not in trio/tests. For now there's some
-# copy-paste...
-#
-# this stuff should become a proper pytest plugin
-
 import pytest
 import inspect
 
diff --git a/trio/tests/test_abc.py b/trio/_tests/test_abc.py
similarity index 100%
rename from trio/tests/test_abc.py
rename to trio/_tests/test_abc.py
diff --git a/trio/tests/test_channel.py b/trio/_tests/test_channel.py
similarity index 100%
rename from trio/tests/test_channel.py
rename to trio/_tests/test_channel.py
diff --git a/trio/tests/test_contextvars.py b/trio/_tests/test_contextvars.py
similarity index 100%
rename from trio/tests/test_contextvars.py
rename to trio/_tests/test_contextvars.py
diff --git a/trio/tests/test_deprecate.py b/trio/_tests/test_deprecate.py
similarity index 88%
rename from trio/tests/test_deprecate.py
rename to trio/_tests/test_deprecate.py
index e5e1da8c5f..856ff20673 100644
--- a/trio/tests/test_deprecate.py
+++ b/trio/_tests/test_deprecate.py
@@ -241,3 +241,32 @@ def test_module_with_deprecations(recwarn_always):
 
     with pytest.raises(AttributeError):
         module_with_deprecations.asdf
+
+
+def test_tests_is_deprecated1() -> None:
+    with pytest.warns(TrioDeprecationWarning):
+        from trio import tests  # warning on import
+
+    # warning on access of any member
+    with pytest.warns(TrioDeprecationWarning):
+        assert tests.test_abc  # type: ignore[attr-defined]
+
+
+def test_tests_is_deprecated2() -> None:
+    # warning on direct import of test since that accesses `__spec__`
+    with pytest.warns(TrioDeprecationWarning):
+        import trio.tests
+
+    with pytest.warns(TrioDeprecationWarning):
+        assert trio.tests.test_deprecate  # type: ignore[attr-defined]
+
+
+def test_tests_is_deprecated3() -> None:
+    import trio
+
+    # no warning on accessing the submodule
+    assert trio.tests
+
+    # only when accessing a submodule member
+    with pytest.warns(TrioDeprecationWarning):
+        assert trio.tests.test_abc  # type: ignore[attr-defined]
diff --git a/trio/tests/test_dtls.py b/trio/_tests/test_dtls.py
similarity index 99%
rename from trio/tests/test_dtls.py
rename to trio/_tests/test_dtls.py
index 1420ea43d1..445ea4d1fd 100644
--- a/trio/tests/test_dtls.py
+++ b/trio/_tests/test_dtls.py
@@ -11,7 +11,7 @@
 from OpenSSL import SSL
 
 from trio.testing._fake_net import FakeNet
-from .._core.tests.tutil import slow, binds_ipv6, gc_collect_harder
+from .._core._tests.tutil import slow, binds_ipv6, gc_collect_harder
 
 ca = trustme.CA()
 server_cert = ca.issue_cert("example.com")
diff --git a/trio/tests/test_exports.py b/trio/_tests/test_exports.py
similarity index 96%
rename from trio/tests/test_exports.py
rename to trio/_tests/test_exports.py
index 8eb1131ee4..2fd8362193 100644
--- a/trio/tests/test_exports.py
+++ b/trio/_tests/test_exports.py
@@ -13,10 +13,10 @@
 
 import trio
 import trio.testing
-from trio.tests.conftest import RUN_SLOW
 
 from .. import _core, _util
-from .._core.tests.tutil import slow
+from .._core._tests.tutil import slow
+from .pytest_plugin import RUN_SLOW
 
 
 def test_core_is_properly_reexported():
@@ -24,7 +24,7 @@ def test_core_is_properly_reexported():
     # three modules:
     sources = [trio, trio.lowlevel, trio.testing]
     for symbol in dir(_core):
-        if symbol.startswith("_") or symbol == "tests":
+        if symbol.startswith("_"):
             continue
         found = 0
         for source in sources:
@@ -47,10 +47,6 @@ def public_modules(module):
             continue
         if class_ is module:  # pragma: no cover
             continue
-        # We should rename the trio.tests module (#274), but until then we use
-        # a special-case hack:
-        if class_.__name__ == "trio.tests":
-            continue
         yield from public_modules(class_)
 
 
@@ -83,10 +79,9 @@ def no_underscores(symbols):
 
     runtime_names = no_underscores(dir(module))
 
-    # We should rename the trio.tests module (#274), but until then we use a
-    # special-case hack:
+    # ignore deprecated module `tests` being invisible
     if modname == "trio":
-        runtime_names.remove("tests")
+        runtime_names.discard("tests")
 
     if tool == "pylint":
         from pylint.lint import PyLinter
@@ -142,6 +137,10 @@ def no_underscores(symbols):
     #   static analysis (e.g. in trio.socket or trio.lowlevel)
     # So we check that the runtime names are a subset of the static names.
     missing_names = runtime_names - static_names
+
+    # ignore warnings about deprecated module tests
+    missing_names -= {"tests"}
+
     if missing_names:  # pragma: no cover
         print(f"{tool} can't see the following names in {modname}:")
         print()
diff --git a/trio/tests/test_fakenet.py b/trio/_tests/test_fakenet.py
similarity index 100%
rename from trio/tests/test_fakenet.py
rename to trio/_tests/test_fakenet.py
diff --git a/trio/tests/test_file_io.py b/trio/_tests/test_file_io.py
similarity index 100%
rename from trio/tests/test_file_io.py
rename to trio/_tests/test_file_io.py
diff --git a/trio/tests/test_highlevel_generic.py b/trio/_tests/test_highlevel_generic.py
similarity index 100%
rename from trio/tests/test_highlevel_generic.py
rename to trio/_tests/test_highlevel_generic.py
diff --git a/trio/tests/test_highlevel_open_tcp_listeners.py b/trio/_tests/test_highlevel_open_tcp_listeners.py
similarity index 99%
rename from trio/tests/test_highlevel_open_tcp_listeners.py
rename to trio/_tests/test_highlevel_open_tcp_listeners.py
index 0c38b4ca69..4942f94d38 100644
--- a/trio/tests/test_highlevel_open_tcp_listeners.py
+++ b/trio/_tests/test_highlevel_open_tcp_listeners.py
@@ -11,7 +11,7 @@
 from trio import open_tcp_listeners, serve_tcp, SocketListener, open_tcp_stream
 from trio.testing import open_stream_to_socket_listener
 from .. import socket as tsocket
-from .._core.tests.tutil import slow, creates_ipv6, binds_ipv6
+from .._core._tests.tutil import slow, creates_ipv6, binds_ipv6
 
 if sys.version_info < (3, 11):
     from exceptiongroup import BaseExceptionGroup
diff --git a/trio/tests/test_highlevel_open_tcp_stream.py b/trio/_tests/test_highlevel_open_tcp_stream.py
similarity index 100%
rename from trio/tests/test_highlevel_open_tcp_stream.py
rename to trio/_tests/test_highlevel_open_tcp_stream.py
diff --git a/trio/tests/test_highlevel_open_unix_stream.py b/trio/_tests/test_highlevel_open_unix_stream.py
similarity index 100%
rename from trio/tests/test_highlevel_open_unix_stream.py
rename to trio/_tests/test_highlevel_open_unix_stream.py
diff --git a/trio/tests/test_highlevel_serve_listeners.py b/trio/_tests/test_highlevel_serve_listeners.py
similarity index 100%
rename from trio/tests/test_highlevel_serve_listeners.py
rename to trio/_tests/test_highlevel_serve_listeners.py
diff --git a/trio/tests/test_highlevel_socket.py b/trio/_tests/test_highlevel_socket.py
similarity index 100%
rename from trio/tests/test_highlevel_socket.py
rename to trio/_tests/test_highlevel_socket.py
diff --git a/trio/tests/test_highlevel_ssl_helpers.py b/trio/_tests/test_highlevel_ssl_helpers.py
similarity index 100%
rename from trio/tests/test_highlevel_ssl_helpers.py
rename to trio/_tests/test_highlevel_ssl_helpers.py
diff --git a/trio/tests/test_path.py b/trio/_tests/test_path.py
similarity index 100%
rename from trio/tests/test_path.py
rename to trio/_tests/test_path.py
diff --git a/trio/tests/test_scheduler_determinism.py b/trio/_tests/test_scheduler_determinism.py
similarity index 100%
rename from trio/tests/test_scheduler_determinism.py
rename to trio/_tests/test_scheduler_determinism.py
diff --git a/trio/tests/test_signals.py b/trio/_tests/test_signals.py
similarity index 100%
rename from trio/tests/test_signals.py
rename to trio/_tests/test_signals.py
diff --git a/trio/tests/test_socket.py b/trio/_tests/test_socket.py
similarity index 99%
rename from trio/tests/test_socket.py
rename to trio/_tests/test_socket.py
index db21096fac..9aa18dc469 100644
--- a/trio/tests/test_socket.py
+++ b/trio/_tests/test_socket.py
@@ -8,7 +8,7 @@
 import inspect
 import tempfile
 import sys as _sys
-from .._core.tests.tutil import creates_ipv6, binds_ipv6
+from .._core._tests.tutil import creates_ipv6, binds_ipv6
 from .. import _core
 from .. import _socket as _tsocket
 from .. import socket as tsocket
diff --git a/trio/tests/test_ssl.py b/trio/_tests/test_ssl.py
similarity index 99%
rename from trio/tests/test_ssl.py
rename to trio/_tests/test_ssl.py
index 26e107e08f..7c63da56e8 100644
--- a/trio/tests/test_ssl.py
+++ b/trio/_tests/test_ssl.py
@@ -26,7 +26,7 @@
 from .._ssl import SSLStream, SSLListener, NeedHandshakeError, _is_eof
 from .._util import ConflictDetector
 
-from .._core.tests.tutil import slow
+from .._core._tests.tutil import slow
 
 from ..testing import (
     assert_checkpoints,
diff --git a/trio/tests/test_subprocess.py b/trio/_tests/test_subprocess.py
similarity index 99%
rename from trio/tests/test_subprocess.py
rename to trio/_tests/test_subprocess.py
index e2d66f654d..4dfaef4c7f 100644
--- a/trio/tests/test_subprocess.py
+++ b/trio/_tests/test_subprocess.py
@@ -20,7 +20,7 @@
     sleep,
     sleep_forever,
 )
-from .._core.tests.tutil import skip_if_fbsd_pipes_broken, slow
+from .._core._tests.tutil import skip_if_fbsd_pipes_broken, slow
 from ..lowlevel import open_process
 from ..testing import assert_no_checkpoints, wait_all_tasks_blocked
 
diff --git a/trio/tests/test_sync.py b/trio/_tests/test_sync.py
similarity index 100%
rename from trio/tests/test_sync.py
rename to trio/_tests/test_sync.py
diff --git a/trio/tests/test_testing.py b/trio/_tests/test_testing.py
similarity index 99%
rename from trio/tests/test_testing.py
rename to trio/_tests/test_testing.py
index a2dba728d5..a9cc00684d 100644
--- a/trio/tests/test_testing.py
+++ b/trio/_tests/test_testing.py
@@ -4,7 +4,7 @@
 
 import pytest
 
-from .._core.tests.tutil import can_bind_ipv6
+from .._core._tests.tutil import can_bind_ipv6
 from .. import sleep
 from .. import _core
 from .._highlevel_generic import aclose_forcefully
diff --git a/trio/tests/test_threads.py b/trio/_tests/test_threads.py
similarity index 99%
rename from trio/tests/test_threads.py
rename to trio/_tests/test_threads.py
index ce852d4612..21eb7b12e8 100644
--- a/trio/tests/test_threads.py
+++ b/trio/_tests/test_threads.py
@@ -14,8 +14,8 @@
 from trio._core import TrioToken, current_trio_token
 
 from .. import CapacityLimiter, Event, _core, sleep
-from .._core.tests.test_ki import ki_self
-from .._core.tests.tutil import buggy_pypy_asyncgens
+from .._core._tests.test_ki import ki_self
+from .._core._tests.tutil import buggy_pypy_asyncgens
 from .._threads import (
     current_default_thread_limiter,
     from_thread_run,
@@ -168,7 +168,7 @@ async def main():
 
 
 async def test_named_thread():
-    ending = " from trio.tests.test_threads.test_named_thread"
+    ending = " from trio._tests.test_threads.test_named_thread"
 
     def inner(name="inner" + ending) -> threading.Thread:
         assert threading.current_thread().name == name
@@ -248,7 +248,7 @@ def f(name: str) -> Callable[[None], threading.Thread]:
         return partial(inner, name)
 
     # test defaults
-    default = "None from trio.tests.test_threads.test_named_thread"
+    default = "None from trio._tests.test_threads.test_named_thread"
     await to_thread_run_sync(f(default))
     await to_thread_run_sync(f(default), thread_name=None)
 
diff --git a/trio/tests/test_timeouts.py b/trio/_tests/test_timeouts.py
similarity index 98%
rename from trio/tests/test_timeouts.py
rename to trio/_tests/test_timeouts.py
index 382c015b1d..c817c49588 100644
--- a/trio/tests/test_timeouts.py
+++ b/trio/_tests/test_timeouts.py
@@ -2,7 +2,7 @@
 import pytest
 import time
 
-from .._core.tests.tutil import slow
+from .._core._tests.tutil import slow
 from .. import _core
 from ..testing import assert_checkpoints
 from .._timeouts import *
diff --git a/trio/tests/test_tracing.py b/trio/_tests/test_tracing.py
similarity index 100%
rename from trio/tests/test_tracing.py
rename to trio/_tests/test_tracing.py
diff --git a/trio/tests/test_unix_pipes.py b/trio/_tests/test_unix_pipes.py
similarity index 99%
rename from trio/tests/test_unix_pipes.py
rename to trio/_tests/test_unix_pipes.py
index cf98942ea4..2109ab8dd2 100644
--- a/trio/tests/test_unix_pipes.py
+++ b/trio/_tests/test_unix_pipes.py
@@ -6,7 +6,7 @@
 
 import pytest
 
-from .._core.tests.tutil import gc_collect_harder, skip_if_fbsd_pipes_broken
+from .._core._tests.tutil import gc_collect_harder, skip_if_fbsd_pipes_broken
 from .. import _core, move_on_after
 from ..testing import wait_all_tasks_blocked, check_one_way_stream
 
diff --git a/trio/tests/test_util.py b/trio/_tests/test_util.py
similarity index 99%
rename from trio/tests/test_util.py
rename to trio/_tests/test_util.py
index 15ab09a80b..9f89a68efe 100644
--- a/trio/tests/test_util.py
+++ b/trio/_tests/test_util.py
@@ -5,7 +5,7 @@
 
 import trio
 from .. import _core
-from .._core.tests.tutil import (
+from .._core._tests.tutil import (
     ignore_coroutine_never_awaited_warnings,
     create_asyncio_future_in_new_loop,
 )
diff --git a/trio/tests/test_wait_for_object.py b/trio/_tests/test_wait_for_object.py
similarity index 99%
rename from trio/tests/test_wait_for_object.py
rename to trio/_tests/test_wait_for_object.py
index 38acfa802d..54291444a0 100644
--- a/trio/tests/test_wait_for_object.py
+++ b/trio/_tests/test_wait_for_object.py
@@ -6,7 +6,7 @@
 # Mark all the tests in this file as being windows-only
 pytestmark = pytest.mark.skipif(not on_windows, reason="windows only")
 
-from .._core.tests.tutil import slow
+from .._core._tests.tutil import slow
 import trio
 from .. import _core
 from .. import _timeouts
diff --git a/trio/tests/test_windows_pipes.py b/trio/_tests/test_windows_pipes.py
similarity index 98%
rename from trio/tests/test_windows_pipes.py
rename to trio/_tests/test_windows_pipes.py
index 2bcc64a072..4443cc0a2f 100644
--- a/trio/tests/test_windows_pipes.py
+++ b/trio/_tests/test_windows_pipes.py
@@ -8,7 +8,7 @@
 
 import pytest
 
-from .._core.tests.tutil import gc_collect_harder
+from .._core._tests.tutil import gc_collect_harder
 from .. import _core, move_on_after
 from ..testing import wait_all_tasks_blocked, check_one_way_stream
 
diff --git a/trio/tests/tools/__init__.py b/trio/_tests/tools/__init__.py
similarity index 100%
rename from trio/tests/tools/__init__.py
rename to trio/_tests/tools/__init__.py
diff --git a/trio/tests/tools/test_gen_exports.py b/trio/_tests/tools/test_gen_exports.py
similarity index 100%
rename from trio/tests/tools/test_gen_exports.py
rename to trio/_tests/tools/test_gen_exports.py
diff --git a/trio/tests.py b/trio/tests.py
new file mode 100644
index 0000000000..f1940a6929
--- /dev/null
+++ b/trio/tests.py
@@ -0,0 +1,38 @@
+import importlib
+import sys
+from typing import Any
+
+from . import _tests
+from ._deprecate import warn_deprecated
+
+warn_deprecated(
+    "trio.tests",
+    "0.24.0",
+    instead="trio._tests",
+    issue="https://github.com/python-trio/trio/issues/274",
+)
+
+
+# This won't give deprecation warning on import, but will give a warning on use of any
+# attribute in tests, and static analysis tools will also not see any content inside.
+class TestsDeprecationWrapper:
+    __name__ = "trio.tests"
+
+    def __getattr__(self, attr: str) -> Any:
+        warn_deprecated(
+            f"trio.tests.{attr}",
+            "0.24.0",
+            instead=f"trio._tests.{attr}",
+            issue="https://github.com/python-trio/trio/issues/274",
+        )
+
+        # needed to access e.g. trio._tests.tools, although pytest doesn't need it
+        if not hasattr(_tests, attr):  # pragma: no cover
+            importlib.import_module(f"trio._tests.{attr}", "trio._tests")
+            return attr
+
+        return getattr(_tests, attr)
+
+
+# https://stackoverflow.com/questions/2447353/getattr-on-a-module
+sys.modules[__name__] = TestsDeprecationWrapper()  # type: ignore[assignment]