diff --git a/Lib/test/test_capi/test_buffer.py b/Lib/test/test_capi/test_buffer.py
new file mode 100644
index 000000000000000..665a22ca0a3e514
--- /dev/null
+++ b/Lib/test/test_capi/test_buffer.py
@@ -0,0 +1,94 @@
+import unittest
+from test.support import import_helper
+
+_testlimitedcapi = import_helper.import_module('_testlimitedcapi')
+_testbuffer = import_helper.import_module('_testbuffer')
+from _testbuffer import ndarray, ND_WRITABLE, ND_FORTRAN
+
+
+class CAPITest(unittest.TestCase):
+    def test_object_copydata(self):
+        # Test PyObject_CopyData()
+        copydata = _testlimitedcapi.object_copydata
+
+        dest = bytearray(b'xyz')
+        self.assertEqual(copydata(dest, b'abc'), 0)
+        self.assertEqual(dest, b'abc')
+
+        dest = bytearray(5)
+        self.assertEqual(copydata(dest, memoryview(b'abc')), 0)
+        self.assertEqual(dest, b'abc\0\0')
+
+        dest = bytearray()
+        self.assertEqual(copydata(dest, b''), 0)
+        self.assertEqual(dest, b'')
+
+        # Non-contiguous source
+        dest = bytearray(4)
+        self.assertEqual(copydata(dest, memoryview(b'abcdefgh')[::2]), 0)
+        self.assertEqual(dest, b'aceg')
+
+        # Non-contiguous destination
+        base = bytearray(b'........')
+        self.assertEqual(copydata(memoryview(base)[::2], b'wxyz'), 0)
+        self.assertEqual(base, b'w.x.y.z.')
+
+        # Destination too small
+        dest = bytearray(b'xy')
+        self.assertRaises(BufferError, copydata, dest, b'abc')
+        self.assertEqual(dest, b'xy')
+
+        # Read-only destination
+        self.assertRaises(BufferError, copydata, b'xyz', b'abc')
+
+        self.assertRaises(TypeError, copydata, bytearray(3), 'abc')
+        self.assertRaises(TypeError, copydata, [], b'')
+        self.assertRaises(TypeError, copydata, 42, b'')
+
+        # CRASHES copydata(NULL, b'abc')
+        # CRASHES copydata(bytearray(3), NULL)
+
+    def test_object_copydata_multidim(self):
+        # Test PyObject_CopyData() with multi-dimensional buffers
+        copydata = _testlimitedcapi.object_copydata
+        items = list(range(12))
+        c_src = ndarray(items, shape=[3, 4], format='B')
+        f_src = ndarray(items, shape=[3, 4], format='B', flags=ND_FORTRAN)
+
+        for src in c_src, f_src:
+            for flags in ND_WRITABLE, ND_WRITABLE|ND_FORTRAN:
+                with self.subTest(src=src.flags, dest=flags):
+                    dest = ndarray([0]*12, shape=[3, 4], format='B',
+                                   flags=flags)
+                    self.assertEqual(copydata(dest, src), 0)
+                    self.assertEqual(dest.tolist(), src.tolist())
+
+        # Multi-byte items
+        src = ndarray([1, -2, 3, -4, 5, -6], shape=[2, 3], format='i')
+        dest = ndarray([0]*6, shape=[2, 3], format='i',
+                       flags=ND_WRITABLE|ND_FORTRAN)
+        self.assertEqual(copydata(dest, src), 0)
+        self.assertEqual(dest.tolist(), [[1, -2, 3], [-4, 5, -6]])
+
+        # Non-contiguous source
+        src = c_src[::2, ::2]
+        dest = ndarray([0]*4, shape=[2, 2], format='B', flags=ND_WRITABLE)
+        self.assertEqual(copydata(dest, src), 0)
+        self.assertEqual(dest.tolist(), [[0, 2], [8, 10]])
+
+    def test_buffer_fillcontiguousstrides(self):
+        # Test PyBuffer_FillContiguousStrides()
+        fill = _testlimitedcapi.buffer_fillcontiguousstrides
+
+        self.assertEqual(fill((2, 3, 4), 8, 'C'), (96, 32, 8))
+        self.assertEqual(fill((2, 3, 4), 8, 'F'), (8, 16, 48))
+        self.assertEqual(fill((5,), 2, 'C'), (2,))
+        self.assertEqual(fill((5,), 2, 'F'), (2,))
+        self.assertEqual(fill((), 4, 'C'), ())
+        self.assertEqual(fill((), 4, 'F'), ())
+        self.assertEqual(fill((2, 0, 3), 4, 'C'), (0, 12, 4))
+        self.assertEqual(fill((2, 0, 3), 4, 'F'), (4, 8, 0))
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Misc/NEWS.d/next/Tests/2026-11-01-11-50-00.gh-issue-160688.Xp4kQw.rst b/Misc/NEWS.d/next/Tests/2026-11-01-11-50-00.gh-issue-160688.Xp4kQw.rst
new file mode 100644
index 000000000000000..e535e38cbcf0a18
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2026-11-01-11-50-00.gh-issue-160688.Xp4kQw.rst
@@ -0,0 +1,2 @@
+Add tests for the C API functions :c:func:`PyObject_CopyData` and
+:c:func:`PyBuffer_FillContiguousStrides`.
diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index d8cd8de10dfe084..a410b0b2bff3b87 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -174,7 +174,7 @@
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c _testinternalcapi/complex.c _testinternalcapi/interpreter.c _testinternalcapi/tokenizer.c _testinternalcapi/tuple.c _testinternalcapi/typecache.c
 @MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/run.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c _testcapi/object.c _testcapi/modsupport.c _testcapi/monitoring.c _testcapi/config.c _testcapi/import.c _testcapi/frame.c _testcapi/type.c _testcapi/function.c _testcapi/module.c _testcapi/weakref.c _testcapi/marshal.c _testcapi/fpcast.c
-@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/capsule.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slice.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c _testlimitedcapi/type.c _testlimitedcapi/hash.c _testlimitedcapi/build.c
+@MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/buffer.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/capsule.c _testlimitedcapi/codec.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/eval.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/import.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/slice.c _testlimitedcapi/slots.c _testlimitedcapi/sys.c _testlimitedcapi/threadstate.c _testlimitedcapi/tuple.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c _testlimitedcapi/version.c _testlimitedcapi/file.c _testlimitedcapi/weakref.c _testlimitedcapi/run.c _testlimitedcapi/type.c _testlimitedcapi/hash.c _testlimitedcapi/build.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c
 
diff --git a/Modules/_testlimitedcapi.c b/Modules/_testlimitedcapi.c
index 1aee3bc9bf3c1df..43ef2e3d06ae1b8 100644
--- a/Modules/_testlimitedcapi.c
+++ b/Modules/_testlimitedcapi.c
@@ -13,6 +13,9 @@ module_exec(PyObject *mod)
     if (_PyTestLimitedCAPI_Init_Abstract(mod) < 0) {
         return -1;
     }
+    if (_PyTestLimitedCAPI_Init_Buffer(mod) < 0) {
+        return -1;
+    }
     if (_PyTestLimitedCAPI_Init_ByteArray(mod) < 0) {
         return -1;
     }
diff --git a/Modules/_testlimitedcapi/buffer.c b/Modules/_testlimitedcapi/buffer.c
new file mode 100644
index 000000000000000..3d19feea1974201
--- /dev/null
+++ b/Modules/_testlimitedcapi/buffer.c
@@ -0,0 +1,86 @@
+#include "pyconfig.h"   // Py_GIL_DISABLED
+#ifdef Py_GIL_DISABLED
+#  define Py_TARGET_ABI3T 0x030f0000
+#else
+   // Need limited C API 3.11 for the buffer protocol
+#  define Py_LIMITED_API 0x030b0000
+#endif
+
+#include "parts.h"
+#include "util.h"
+
+
+static PyObject *
+object_copydata(PyObject *Py_UNUSED(module), PyObject *args)
+{
+    PyObject *dest, *src;
+    if (!PyArg_ParseTuple(args, "OO", &dest, &src)) {
+        return NULL;
+    }
+    RETURN_INT(PyObject_CopyData(dest, src));
+}
+
+static PyObject *
+buffer_fillcontiguousstrides(PyObject *Py_UNUSED(module), PyObject *args)
+{
+    PyObject *shape_obj;
+    int itemsize, order;
+    if (!PyArg_ParseTuple(args, "O!iC", &PyTuple_Type, &shape_obj,
+                          &itemsize, &order))
+    {
+        return NULL;
+    }
+    Py_ssize_t size = PyTuple_Size(shape_obj);
+    if (size < 0) {
+        return NULL;
+    }
+    int nd = (int)size;
+    Py_ssize_t *shape = PyMem_Malloc(size * sizeof(Py_ssize_t));
+    Py_ssize_t *strides = PyMem_Malloc(size * sizeof(Py_ssize_t));
+    if (shape == NULL || strides == NULL) {
+        PyErr_NoMemory();
+        goto error;
+    }
+    for (int k = 0; k < nd; k++) {
+        shape[k] = PyLong_AsSsize_t(PyTuple_GetItem(shape_obj, k));
+        if (shape[k] == -1 && PyErr_Occurred()) {
+            goto error;
+        }
+    }
+
+    PyBuffer_FillContiguousStrides(nd, shape, strides, itemsize, (char)order);
+
+    PyObject *result = PyTuple_New(size);
+    if (result == NULL) {
+        goto error;
+    }
+    for (int k = 0; k < nd; k++) {
+        PyObject *item = PyLong_FromSsize_t(strides[k]);
+        if (item == NULL) {
+            Py_DECREF(result);
+            goto error;
+        }
+        PyTuple_SetItem(result, k, item);
+    }
+    PyMem_Free(shape);
+    PyMem_Free(strides);
+    return result;
+
+error:
+    PyMem_Free(shape);
+    PyMem_Free(strides);
+    return NULL;
+}
+
+
+static PyMethodDef test_methods[] = {
+    {"object_copydata", object_copydata, METH_VARARGS},
+    {"buffer_fillcontiguousstrides", buffer_fillcontiguousstrides, METH_VARARGS},
+    {NULL},
+};
+
+int
+_PyTestLimitedCAPI_Init_Buffer(PyObject *m)
+{
+    return PyModule_AddFunctions(m, test_methods);
+}
diff --git a/Modules/_testlimitedcapi/parts.h b/Modules/_testlimitedcapi/parts.h
index 1e9d140899cecfd..9d34ce087f749d7 100644
--- a/Modules/_testlimitedcapi/parts.h
+++ b/Modules/_testlimitedcapi/parts.h
@@ -25,6 +25,7 @@
 #endif
 
 int _PyTestLimitedCAPI_Init_Abstract(PyObject *module);
+int _PyTestLimitedCAPI_Init_Buffer(PyObject *module);
 int _PyTestLimitedCAPI_Init_ByteArray(PyObject *module);
 int _PyTestLimitedCAPI_Init_Bytes(PyObject *module);
 int _PyTestLimitedCAPI_Init_Capsule(PyObject *module);
diff --git a/PCbuild/_testlimitedcapi.vcxproj b/PCbuild/_testlimitedcapi.vcxproj
index 1a40cd0d2271f5f..e85d69bb2d780b9 100644
--- a/PCbuild/_testlimitedcapi.vcxproj
+++ b/PCbuild/_testlimitedcapi.vcxproj
@@ -95,6 +95,7 @@
   <ItemGroup>
     <ClCompile Include="..\Modules\_testlimitedcapi.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\abstract.c" />
+    <ClCompile Include="..\Modules\_testlimitedcapi\buffer.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\bytearray.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\bytes.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\capsule.c" />
diff --git a/PCbuild/_testlimitedcapi.vcxproj.filters b/PCbuild/_testlimitedcapi.vcxproj.filters
index 1b13da0ebca7ba2..1bd170ad2381705 100644
--- a/PCbuild/_testlimitedcapi.vcxproj.filters
+++ b/PCbuild/_testlimitedcapi.vcxproj.filters
@@ -10,6 +10,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="..\Modules\_testlimitedcapi\abstract.c" />
+    <ClCompile Include="..\Modules\_testlimitedcapi\buffer.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\bytearray.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\bytes.c" />
     <ClCompile Include="..\Modules\_testlimitedcapi\capsule.c" />