Add java tests

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/ProcessCameraProviderHostApiImpl.java

@@ -9,7 +9,6 @@
 import androidx.camera.core.Camera;
 import androidx.camera.core.CameraInfo;
 import androidx.camera.core.CameraSelector;
-import androidx.camera.core.Preview;
 import androidx.camera.core.UseCase;
 import androidx.camera.lifecycle.ProcessCameraProvider;
 import androidx.core.content.ContextCompat;
@@ -95,7 +94,8 @@ public List<Long> getAvailableCameraInfos(@NonNull Long identifier) {
 
   /**
    * Binds specified {@code UseCase}s to the lifecycle of the {@code LifecycleOwner} that
-   * corresponds to this instance.
+   * corresponds to this instance and returns the instance of the {@code Camera} whose lifecycle
+   * that {@code LifecycleOwner} reflects.
    */
   @Override
   public Long bindToLifecycle(
@@ -111,20 +111,15 @@ public Long bindToLifecycle(
       useCases[i] = (UseCase) instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue());
     }
 
-    if (lifecycleOwner != null) {
-      Camera camera =
-          processCameraProvider.bindToLifecycle(
-              (LifecycleOwner) lifecycleOwner, cameraSelector, useCases);
+    Camera camera =
+        processCameraProvider.bindToLifecycle(
+            (LifecycleOwner) lifecycleOwner, cameraSelector, useCases);
 
-      final CameraFlutterApiImpl camraFlutterApi =
-          new CameraFlutterApiImpl(binaryMessenger, instanceManager);
-      camraFlutterApi.create(camera, result -> {});
+    final CameraFlutterApiImpl camraFlutterApi =
+        new CameraFlutterApiImpl(binaryMessenger, instanceManager);
+    camraFlutterApi.create(camera, result -> {});
 
-      return instanceManager.getIdentifierForStrongReference(camera);
-    } else {
-      // TODO(camsim99): Throw error here?
-      return null;
-    }
+    return instanceManager.getIdentifierForStrongReference(camera);
   }
 
   @Override
@@ -133,7 +128,7 @@ public void unbind(@NonNull Long identifier, @NonNull List<Long> useCaseIds) {
         (ProcessCameraProvider) instanceManager.getInstance(identifier);
     UseCase[] useCases = new UseCase[useCaseIds.size()];
     for (int i = 0; i < useCaseIds.size(); i++) {
-      useCases[i] = (Preview) instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue());
+      useCases[i] = (UseCase) instanceManager.getInstance(((Number) useCaseIds.get(i)).longValue());
     }
     processCameraProvider.unbind(useCases);
   }

packages/camera/camera_android_camerax/android/src/test/java/io/flutter/plugins/camerax/CameraTest.java

@@ -0,0 +1,49 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.camerax;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+import androidx.camera.core.Camera;
+import io.flutter.plugin.common.BinaryMessenger;
+import java.util.Objects;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnit;
+import org.mockito.junit.MockitoRule;
+import org.robolectric.RobolectricTestRunner;
+
+@RunWith(RobolectricTestRunner.class)
+public class CameraTest {
+  @Rule public MockitoRule mockitoRule = MockitoJUnit.rule();
+
+  @Mock public BinaryMessenger mockBinaryMessenger;
+  @Mock public Camera camera;
+
+  InstanceManager testInstanceManager;
+
+  @Before
+  public void setUp() {
+    testInstanceManager = InstanceManager.open(identifier -> {});
+  }
+
+  @Test
+  public void flutterApiCreateTest() {
+    final CameraFlutterApiImpl spyFlutterApi =
+        spy(new CameraFlutterApiImpl(mockBinaryMessenger, testInstanceManager));
+
+    spyFlutterApi.create(camera, reply -> {});
+
+    final long identifier =
+        Objects.requireNonNull(testInstanceManager.getIdentifierForStrongReference(camera));
+    verify(spyFlutterApi).create(eq(identifier), any());
+  }
+}

packages/camera/camera_android_camerax/android/src/test/java/io/flutter/plugins/camerax/ProcessCameraProviderTest.java

@@ -13,8 +13,12 @@
 import static org.mockito.Mockito.when;
 
 import android.content.Context;
+import androidx.camera.core.Camera;
 import androidx.camera.core.CameraInfo;
+import androidx.camera.core.CameraSelector;
+import androidx.camera.core.UseCase;
 import androidx.camera.lifecycle.ProcessCameraProvider;
+import androidx.lifecycle.LifecycleOwner;
 import androidx.test.core.app.ApplicationProvider;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
@@ -99,6 +103,58 @@ public void getAvailableCameraInfosTest() {
     verify(processCameraProvider).getAvailableCameraInfos();
   }
 
+  @Test
+  public void bindToLifecycleTest() {
+    final ProcessCameraProviderHostApiImpl processCameraProviderHostApi =
+        new ProcessCameraProviderHostApiImpl(mockBinaryMessenger, testInstanceManager, context);
+    final Camera mockCamera = mock(Camera.class);
+    final CameraSelector mockCameraSelector = mock(CameraSelector.class);
+    final UseCase mockUseCase = mock(UseCase.class);
+    UseCase[] mockUseCases = new UseCase[] {mockUseCase};
+
+    LifecycleOwner mockLifecycleOwner = mock(LifecycleOwner.class);
+    processCameraProviderHostApi.setLifecycleOwner(mockLifecycleOwner);
+
+    testInstanceManager.addDartCreatedInstance(processCameraProvider, 0);
+    testInstanceManager.addDartCreatedInstance(mockCameraSelector, 1);
+    testInstanceManager.addDartCreatedInstance(mockUseCase, 2);
+    testInstanceManager.addDartCreatedInstance(mockCamera, 3);
+
+    when(processCameraProvider.bindToLifecycle(
+            mockLifecycleOwner, mockCameraSelector, mockUseCases))
+        .thenReturn(mockCamera);
+
+    assertEquals(
+        processCameraProviderHostApi.bindToLifecycle(0L, 1L, Arrays.asList(2L)), Long.valueOf(3));
+    verify(processCameraProvider)
+        .bindToLifecycle(mockLifecycleOwner, mockCameraSelector, mockUseCases);
+  }
+
+  @Test
+  public void unbindTest() {
+    final ProcessCameraProviderHostApiImpl processCameraProviderHostApi =
+        new ProcessCameraProviderHostApiImpl(mockBinaryMessenger, testInstanceManager, context);
+    final UseCase mockUseCase = mock(UseCase.class);
+    UseCase[] mockUseCases = new UseCase[] {mockUseCase};
+
+    testInstanceManager.addDartCreatedInstance(processCameraProvider, 0);
+    testInstanceManager.addDartCreatedInstance(mockUseCase, 1);
+
+    processCameraProviderHostApi.unbind(0L, Arrays.asList(1L));
+    verify(processCameraProvider).unbind(mockUseCases);
+  }
+
+  @Test
+  public void unbindAllTest() {
+    final ProcessCameraProviderHostApiImpl processCameraProviderHostApi =
+        new ProcessCameraProviderHostApiImpl(mockBinaryMessenger, testInstanceManager, context);
+
+    testInstanceManager.addDartCreatedInstance(processCameraProvider, 0);
+
+    processCameraProviderHostApi.unbindAll(0L);
+    verify(processCameraProvider).unbindAll();
+  }
+
   @Test
   public void flutterApiCreateTest() {
     final ProcessCameraProviderFlutterApiImpl spyFlutterApi =