diff --git a/packages/react-native/ReactCommon/react/renderer/mounting/tests/OrderIndexTest.cpp b/packages/react-native/ReactCommon/react/renderer/mounting/tests/OrderIndexTest.cpp
new file mode 100644
index 00000000000..804287cc133
--- /dev/null
+++ b/packages/react-native/ReactCommon/react/renderer/mounting/tests/OrderIndexTest.cpp
@@ -0,0 +1,244 @@
+/*
+ * 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 <algorithm>
+#include <memory>
+
+#include <gtest/gtest.h>
+
+#include <react/renderer/componentregistry/ComponentDescriptorProviderRegistry.h>
+#include <react/renderer/components/root/RootComponentDescriptor.h>
+#include <react/renderer/components/scrollview/ScrollViewComponentDescriptor.h>
+#include <react/renderer/components/view/ViewComponentDescriptor.h>
+#include <react/renderer/element/ComponentBuilder.h>
+#include <react/renderer/element/Element.h>
+#include <react/renderer/element/testUtils.h>
+#include <react/renderer/mounting/Differentiator.h>
+#include <react/renderer/mounting/ShadowViewMutation.h>
+#include <react/renderer/mounting/stubs.h>
+
+namespace facebook::react {
+
+class OrderIndexTest : public ::testing::Test {
+ protected:
+  ComponentBuilder builder_;
+  std::shared_ptr<RootShadowNode> rootShadowNode_;
+  std::shared_ptr<ViewShadowNode> nodeA_;
+  std::shared_ptr<ViewShadowNode> nodeB_;
+  std::shared_ptr<ViewShadowNode> nodeC_;
+  std::shared_ptr<ViewShadowNode> nodeD_;
+
+  std::shared_ptr<RootShadowNode> currentRootShadowNode_;
+  StubViewTree currentStubViewTree_;
+
+  OrderIndexTest() : builder_(simpleComponentBuilder()) {
+    auto element = Element<RootShadowNode>()
+                       .reference(rootShadowNode_)
+                       .tag(1)
+                       .children({
+                           Element<ViewShadowNode>().tag(2).reference(nodeA_),
+                           Element<ViewShadowNode>().tag(3).reference(nodeB_),
+                           Element<ViewShadowNode>().tag(4).reference(nodeC_),
+                           Element<ViewShadowNode>().tag(5).reference(nodeD_),
+                       });
+
+    builder_.build(element);
+
+    mutateViewShadowNodeProps_(nodeA_, [](ViewProps& props) {
+      auto& yogaStyle = props.yogaStyle;
+      yogaStyle.setPositionType(yoga::PositionType::Relative);
+      props.backgroundColor = blackColor(); // to ensure it won't get flattened
+    });
+    mutateViewShadowNodeProps_(nodeB_, [](ViewProps& props) {
+      auto& yogaStyle = props.yogaStyle;
+      yogaStyle.setPositionType(yoga::PositionType::Relative);
+      props.backgroundColor = blackColor(); // to ensure it won't get flattened
+    });
+    mutateViewShadowNodeProps_(nodeC_, [](ViewProps& props) {
+      auto& yogaStyle = props.yogaStyle;
+      yogaStyle.setPositionType(yoga::PositionType::Relative);
+      props.backgroundColor = blackColor(); // to ensure it won't get flattened
+    });
+    mutateViewShadowNodeProps_(nodeD_, [](ViewProps& props) {
+      auto& yogaStyle = props.yogaStyle;
+      yogaStyle.setPositionType(yoga::PositionType::Relative);
+      props.backgroundColor = blackColor(); // to ensure it won't get flattened
+    });
+
+    currentRootShadowNode_ = rootShadowNode_;
+    currentRootShadowNode_->layoutIfNeeded();
+    currentStubViewTree_ =
+        buildStubViewTreeWithoutUsingDifferentiator(*currentRootShadowNode_);
+  }
+
+  void mutateViewShadowNodeProps_(
+      const std::shared_ptr<ViewShadowNode>& node,
+      std::function<void(ViewProps& props)> callback) {
+    rootShadowNode_ =
+        std::static_pointer_cast<RootShadowNode>(rootShadowNode_->cloneTree(
+            node->getFamily(), [&](const ShadowNode& oldShadowNode) {
+              auto viewProps = std::make_shared<ViewShadowNodeProps>();
+              callback(*viewProps);
+              return oldShadowNode.clone(ShadowNodeFragment{viewProps});
+            }));
+  }
+
+  void testViewTree_(
+      const std::function<void(StubViewTree const& viewTree)>& callback) {
+    rootShadowNode_->layoutIfNeeded();
+
+    callback(buildStubViewTreeUsingDifferentiator(*rootShadowNode_));
+
+    auto mutations =
+        calculateShadowViewMutations(*currentRootShadowNode_, *rootShadowNode_);
+    currentRootShadowNode_ = rootShadowNode_;
+    currentStubViewTree_.mutate(mutations);
+    callback(currentStubViewTree_);
+  }
+};
+
+TEST_F(OrderIndexTest, defaultOrderIsDocumentOrder) {
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeA_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeB_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeC_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeD_->getTag());
+  });
+}
+
+TEST_F(OrderIndexTest, basicZIndex) {
+  mutateViewShadowNodeProps_(
+      nodeA_, [](ViewProps& props) { props.zIndex = 5; });
+  mutateViewShadowNodeProps_(
+      nodeB_, [](ViewProps& props) { props.zIndex = 10; });
+  mutateViewShadowNodeProps_(
+      nodeC_, [](ViewProps& props) { props.zIndex = 1; });
+  mutateViewShadowNodeProps_(
+      nodeD_, [](ViewProps& props) { props.zIndex = 2; });
+
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeC_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeD_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeA_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeB_->getTag());
+  });
+}
+
+TEST_F(OrderIndexTest, negativeZIndex) {
+  mutateViewShadowNodeProps_(
+      nodeA_, [](ViewProps& props) { props.zIndex = 5; });
+  mutateViewShadowNodeProps_(
+      nodeB_, [](ViewProps& props) { props.zIndex = -10; });
+  mutateViewShadowNodeProps_(
+      nodeC_, [](ViewProps& props) { props.zIndex = -1; });
+  mutateViewShadowNodeProps_(
+      nodeD_, [](ViewProps& props) { props.zIndex = 2; });
+
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeB_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeC_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeD_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeA_->getTag());
+  });
+}
+
+TEST_F(OrderIndexTest, zeroZIndex) {
+  mutateViewShadowNodeProps_(
+      nodeC_, [](ViewProps& props) { props.zIndex = 0; });
+  mutateViewShadowNodeProps_(
+      nodeD_, [](ViewProps& props) { props.zIndex = 0; });
+
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeA_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeB_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeC_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeD_->getTag());
+  });
+}
+
+TEST_F(OrderIndexTest, staticBehindNonStatic) {
+  mutateViewShadowNodeProps_(nodeB_, [](ViewProps& props) {
+    auto& yogaStyle = props.yogaStyle;
+    yogaStyle.setPositionType(yoga::PositionType::Static);
+    props.backgroundColor = blackColor();
+  });
+  mutateViewShadowNodeProps_(nodeD_, [](ViewProps& props) {
+    auto& yogaStyle = props.yogaStyle;
+    yogaStyle.setPositionType(yoga::PositionType::Static);
+    props.backgroundColor = blackColor();
+  });
+
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeB_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeD_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeA_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeC_->getTag());
+  });
+}
+
+TEST_F(OrderIndexTest, zIndexStaticBehindNonStatic) {
+  mutateViewShadowNodeProps_(
+      nodeB_, [](ViewProps& props) { props.zIndex = 5; });
+  mutateViewShadowNodeProps_(
+      nodeC_, [](ViewProps& props) { props.zIndex = -1; });
+  mutateViewShadowNodeProps_(nodeD_, [](ViewProps& props) {
+    auto& yogaStyle = props.yogaStyle;
+    yogaStyle.setPositionType(yoga::PositionType::Static);
+    props.backgroundColor = blackColor();
+  });
+
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeC_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeD_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeA_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeB_->getTag());
+  });
+}
+
+TEST_F(OrderIndexTest, staticDoesNotGetZIndex) {
+  mutateViewShadowNodeProps_(nodeB_, [](ViewProps& props) {
+    auto& yogaStyle = props.yogaStyle;
+    yogaStyle.setPositionType(yoga::PositionType::Static);
+    props.backgroundColor = blackColor();
+    props.zIndex = 5;
+  });
+  mutateViewShadowNodeProps_(nodeD_, [](ViewProps& props) {
+    auto& yogaStyle = props.yogaStyle;
+    yogaStyle.setPositionType(yoga::PositionType::Static);
+    props.backgroundColor = blackColor();
+    props.zIndex = -5;
+  });
+
+  testViewTree_([this](const StubViewTree& viewTree) {
+    EXPECT_EQ(viewTree.size(), 5);
+    EXPECT_EQ(viewTree.getRootStubView().children.size(), 4);
+
+    EXPECT_EQ(viewTree.getRootStubView().children.at(0)->tag, nodeB_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(1)->tag, nodeD_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(2)->tag, nodeA_->getTag());
+    EXPECT_EQ(viewTree.getRootStubView().children.at(3)->tag, nodeC_->getTag());
+  });
+}
+} // namespace facebook::react