diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/test/MountItemTest.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/test/MountItemTest.cpp
new file mode 100644
index 000000000000..3e3513835545
--- /dev/null
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/test/MountItemTest.cpp
@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <react/fabric/MountItem.h>
+
+#include <gtest/gtest.h>
+
+namespace facebook::react {
+
+namespace {
+
+ShadowView
+makeShadowView(ComponentName componentName, SurfaceId surfaceId, Tag tag) {
+  auto shadowView = ShadowView{};
+  shadowView.componentName = componentName;
+  shadowView.surfaceId = surfaceId;
+  shadowView.tag = tag;
+  return shadowView;
+}
+
+void expectSameShadowViewIdentity(
+    const ShadowView& expected,
+    const ShadowView& actual) {
+  EXPECT_EQ(expected.componentName, actual.componentName);
+  EXPECT_EQ(expected.surfaceId, actual.surfaceId);
+  EXPECT_EQ(expected.tag, actual.tag);
+}
+
+void expectEmptyShadowView(const ShadowView& shadowView) {
+  EXPECT_EQ(nullptr, shadowView.componentName);
+  EXPECT_EQ(SurfaceId{}, shadowView.surfaceId);
+  EXPECT_EQ(Tag{}, shadowView.tag);
+}
+
+} // namespace
+
+class MountItemTest : public ::testing::Test {};
+
+TEST_F(MountItemTest, testCreateAndDeleteUseOppositeShadowViewSlots) {
+  const auto shadowView = makeShadowView("View", /*surfaceId=*/11, /*tag=*/101);
+
+  const auto createItem = CppMountItem::CreateMountItem(shadowView);
+  const auto deleteItem = CppMountItem::DeleteMountItem(shadowView);
+
+  EXPECT_EQ(CppMountItem::Type::Create, createItem.type);
+  expectSameShadowViewIdentity(shadowView, createItem.newChildShadowView);
+  expectEmptyShadowView(createItem.oldChildShadowView);
+  EXPECT_EQ(-1, createItem.index);
+
+  EXPECT_EQ(CppMountItem::Type::Delete, deleteItem.type);
+  expectSameShadowViewIdentity(shadowView, deleteItem.oldChildShadowView);
+  expectEmptyShadowView(deleteItem.newChildShadowView);
+  EXPECT_EQ(-1, deleteItem.index);
+}
+
+TEST_F(MountItemTest, testInsertAndRemovePreserveParentIndexAndChildSlot) {
+  constexpr Tag kParentTag = 501;
+  constexpr int kIndex = 3;
+  const auto shadowView = makeShadowView("Text", /*surfaceId=*/22, /*tag=*/202);
+
+  const auto insertItem =
+      CppMountItem::InsertMountItem(kParentTag, shadowView, kIndex);
+  const auto removeItem =
+      CppMountItem::RemoveMountItem(kParentTag, shadowView, kIndex);
+
+  EXPECT_EQ(CppMountItem::Type::Insert, insertItem.type);
+  EXPECT_EQ(kParentTag, insertItem.parentTag);
+  EXPECT_EQ(kIndex, insertItem.index);
+  expectSameShadowViewIdentity(shadowView, insertItem.newChildShadowView);
+  expectEmptyShadowView(insertItem.oldChildShadowView);
+
+  EXPECT_EQ(CppMountItem::Type::Remove, removeItem.type);
+  EXPECT_EQ(kParentTag, removeItem.parentTag);
+  EXPECT_EQ(kIndex, removeItem.index);
+  expectSameShadowViewIdentity(shadowView, removeItem.oldChildShadowView);
+  expectEmptyShadowView(removeItem.newChildShadowView);
+}
+
+TEST_F(MountItemTest, testUpdatePropsPreservesOldAndNewShadowViews) {
+  const auto oldShadowView =
+      makeShadowView("RawText", /*surfaceId=*/33, /*tag=*/303);
+  const auto newShadowView =
+      makeShadowView("RawText", /*surfaceId=*/33, /*tag=*/404);
+
+  const auto item =
+      CppMountItem::UpdatePropsMountItem(oldShadowView, newShadowView);
+
+  EXPECT_EQ(CppMountItem::Type::UpdateProps, item.type);
+  expectSameShadowViewIdentity(oldShadowView, item.oldChildShadowView);
+  expectSameShadowViewIdentity(newShadowView, item.newChildShadowView);
+  EXPECT_EQ(-1, item.index);
+}
+
+TEST_F(MountItemTest, testUpdateLayoutPreservesParentTagWithShadowView) {
+  constexpr Tag kParentTag = 604;
+  const auto shadowView =
+      makeShadowView("ScrollView", /*surfaceId=*/44, /*tag=*/404);
+
+  const auto item = CppMountItem::UpdateLayoutMountItem(shadowView, kParentTag);
+
+  EXPECT_EQ(CppMountItem::Type::UpdateLayout, item.type);
+  EXPECT_EQ(kParentTag, item.parentTag);
+  expectSameShadowViewIdentity(shadowView, item.newChildShadowView);
+  expectEmptyShadowView(item.oldChildShadowView);
+  EXPECT_EQ(-1, item.index);
+}
+
+TEST_F(MountItemTest, testNonLayoutUpdatesTargetNewShadowViewOnly) {
+  const auto shadowView =
+      makeShadowView("Image", /*surfaceId=*/55, /*tag=*/505);
+
+  const auto stateItem = CppMountItem::UpdateStateMountItem(shadowView);
+  const auto eventEmitterItem =
+      CppMountItem::UpdateEventEmitterMountItem(shadowView);
+  const auto paddingItem = CppMountItem::UpdatePaddingMountItem(shadowView);
+  const auto overflowInsetItem =
+      CppMountItem::UpdateOverflowInsetMountItem(shadowView);
+
+  EXPECT_EQ(CppMountItem::Type::UpdateState, stateItem.type);
+  expectSameShadowViewIdentity(shadowView, stateItem.newChildShadowView);
+  expectEmptyShadowView(stateItem.oldChildShadowView);
+
+  EXPECT_EQ(CppMountItem::Type::UpdateEventEmitter, eventEmitterItem.type);
+  expectSameShadowViewIdentity(shadowView, eventEmitterItem.newChildShadowView);
+  expectEmptyShadowView(eventEmitterItem.oldChildShadowView);
+
+  EXPECT_EQ(CppMountItem::Type::UpdatePadding, paddingItem.type);
+  expectSameShadowViewIdentity(shadowView, paddingItem.newChildShadowView);
+  expectEmptyShadowView(paddingItem.oldChildShadowView);
+
+  EXPECT_EQ(CppMountItem::Type::UpdateOverflowInset, overflowInsetItem.type);
+  expectSameShadowViewIdentity(
+      shadowView, overflowInsetItem.newChildShadowView);
+  expectEmptyShadowView(overflowInsetItem.oldChildShadowView);
+}
+
+} // namespace facebook::react