Convert MountingManagerTest to Kotlin (facebook#44837)

Summary:
Pull Request resolved: facebook#44837

As the title says.

Changelog:
[Internal] [Changed] - Convert MountingManagerTest to Kotlin

Differential Revision: D58290597

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)
+  }
+}