diff --git a/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/MountingManagerTest.java b/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/MountingManagerTest.java
deleted file mode 100644
index a66dca3ff86ca5..00000000000000
--- a/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/MountingManagerTest.java
+++ /dev/null
@@ -1,89 +0,0 @@
-/*
- * 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.
- */
-
-package com.facebook.react.fabric;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-import com.facebook.react.ReactRootView;
-import com.facebook.react.bridge.BridgeReactContext;
-import com.facebook.react.bridge.ReactTestHelper;
-import com.facebook.react.fabric.mounting.MountingManager;
-import com.facebook.react.fabric.mounting.mountitems.MountItem;
-import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsForTests;
-import com.facebook.react.uimanager.IllegalViewOperationException;
-import com.facebook.react.uimanager.ThemedReactContext;
-import com.facebook.react.uimanager.ViewManager;
-import com.facebook.react.uimanager.ViewManagerRegistry;
-import com.facebook.react.views.view.ReactViewManager;
-import java.util.Arrays;
-import java.util.List;
-import java.util.Queue;
-import org.junit.Before;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.robolectric.RobolectricTestRunner;
-import org.robolectric.RuntimeEnvironment;
-
-/** Tests {@link FabricUIManager} */
-@RunWith(RobolectricTestRunner.class)
-public class MountingManagerTest {
-
-  private MountingManager mMountingManager;
-  private MountingManager.MountItemExecutor mMountItemExecutor;
-  private ThemedReactContext mThemedReactContext;
-  private int mNextRootTag = 1;
-
-  @Before
-  public void setUp() {
-    ReactNativeFeatureFlagsForTests.INSTANCE.setUp();
-
-    BridgeReactContext reactContext = new BridgeReactContext(RuntimeEnvironment.application);
-    reactContext.initializeWithInstance(ReactTestHelper.createMockCatalystInstance());
-    mThemedReactContext = new ThemedReactContext(reactContext, reactContext);
-    List<ViewManager> viewManagers = Arrays.<ViewManager>asList(new ReactViewManager());
-    mMountItemExecutor =
-        new MountingManager.MountItemExecutor() {
-          @Override
-          public void executeItems(Queue<MountItem> items) {
-            // no-op
-          }
-        };
-    mMountingManager =
-        new MountingManager(new ViewManagerRegistry(viewManagers), mMountItemExecutor);
-  }
-
-  @Test
-  public void addRootView() {
-    ReactRootView reactRootView = new ReactRootView(mThemedReactContext);
-    int rootReactTag = mNextRootTag++;
-    mMountingManager.startSurface(rootReactTag, mThemedReactContext, reactRootView);
-    assertThat(reactRootView.getId()).isEqualTo(rootReactTag);
-  }
-
-  @Test
-  public void unableToAddRootViewTwice() {
-    ReactRootView reactRootView = new ReactRootView(mThemedReactContext);
-    int rootReactTag = mNextRootTag++;
-    mMountingManager.startSurface(rootReactTag, mThemedReactContext, reactRootView);
-    assertThat(reactRootView.getId()).isEqualTo(rootReactTag);
-
-    // This is now a SoftException because it indicates a race condition in starting
-    // a single surface with a single View, and is concerning but not necessarily fatal.
-    // To be clear: in this case we're still guaranteed a single SurfaceMountingManager
-    // and therefore a single View involved.
-    mMountingManager.startSurface(rootReactTag, mThemedReactContext, reactRootView);
-  }
-
-  @Test(expected = IllegalViewOperationException.class)
-  public void unableToAddHandledRootView() {
-    ReactRootView reactRootView = new ReactRootView(mThemedReactContext);
-    reactRootView.setId(1234567);
-    int rootReactTag = mNextRootTag++;
-    mMountingManager.startSurface(rootReactTag, mThemedReactContext, reactRootView);
-  }
-}
diff --git a/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/MountingManagerTest.kt b/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/MountingManagerTest.kt
new file mode 100644
index 00000000000000..bc67c9f96dd0db
--- /dev/null
+++ b/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/fabric/MountingManagerTest.kt
@@ -0,0 +1,78 @@
+/*
+ * 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.
+ */
+
+package com.facebook.react.fabric
+
+import com.facebook.react.ReactRootView
+import com.facebook.react.bridge.BridgeReactContext
+import com.facebook.react.bridge.ReactTestHelper.createMockCatalystInstance
+import com.facebook.react.fabric.mounting.MountingManager
+import com.facebook.react.fabric.mounting.MountingManager.MountItemExecutor
+import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsForTests
+import com.facebook.react.uimanager.IllegalViewOperationException
+import com.facebook.react.uimanager.ThemedReactContext
+import com.facebook.react.uimanager.ViewManager
+import com.facebook.react.uimanager.ViewManagerRegistry
+import com.facebook.react.views.view.ReactViewManager
+import org.assertj.core.api.Assertions
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.RuntimeEnvironment
+
+/** Tests [FabricUIManager] */
+@RunWith(RobolectricTestRunner::class)
+class MountingManagerTest {
+  private lateinit var mountingManager: MountingManager
+  private lateinit var mountItemExecutor: MountItemExecutor
+  private lateinit var themedReactContext: ThemedReactContext
+  private var nextRootTag = 1
+
+  @Before
+  fun setUp() {
+    ReactNativeFeatureFlagsForTests.setUp()
+    val reactContext = BridgeReactContext(RuntimeEnvironment.getApplication())
+    reactContext.initializeWithInstance(createMockCatalystInstance())
+    themedReactContext = ThemedReactContext(reactContext, reactContext, null, -1)
+    val viewManagers = listOf<ViewManager<*, *>>(ReactViewManager())
+    mountItemExecutor = MountItemExecutor {
+      // no-op
+    }
+    mountingManager = MountingManager(ViewManagerRegistry(viewManagers), mountItemExecutor)
+  }
+
+  @Test
+  fun addRootView() {
+    val reactRootView = ReactRootView(themedReactContext)
+    val rootReactTag = nextRootTag++
+    mountingManager.startSurface(rootReactTag, themedReactContext, reactRootView)
+    Assertions.assertThat(reactRootView.id).isEqualTo(rootReactTag)
+  }
+
+  @Test
+  fun unableToAddRootViewTwice() {
+    val reactRootView = ReactRootView(themedReactContext)
+    val rootReactTag = nextRootTag++
+    mountingManager.startSurface(rootReactTag, themedReactContext, reactRootView)
+    Assertions.assertThat(reactRootView.id).isEqualTo(rootReactTag)
+
+    // This is now a SoftException because it indicates a race condition in starting
+    // a single surface with a single View, and is concerning but not necessarily fatal.
+    // To be clear: in this case we're still guaranteed a single SurfaceMountingManager
+    // and therefore a single View involved.
+    mountingManager.startSurface(rootReactTag, themedReactContext, reactRootView)
+  }
+
+  @Test(expected = IllegalViewOperationException::class)
+  fun unableToAddHandledRootView() {
+    val reactRootView = ReactRootView(themedReactContext)
+    reactRootView.id = 1234567
+    val rootReactTag = nextRootTag++
+    mountingManager.startSurface(rootReactTag, themedReactContext, reactRootView)
+  }
+}