Implement camera startup emulation in FakeCameraSystem

core/camera/build.gradle.kts

@@ -114,6 +114,8 @@ dependencies {
     androidTestImplementation(libs.androidx.rules)
     androidTestImplementation(libs.kotlinx.coroutines.test)
     androidTestImplementation(libs.truth)
+    androidTestImplementation(project(":core:common:testing"))
+    testImplementation(project(":core:camera:testing"))
 
     // Futures
     implementation(libs.futures.ktx)
@@ -124,6 +126,7 @@ dependencies {
     // CameraX
     implementation(libs.camera.core)
     implementation(libs.camera.camera2)
+    implementation(libs.camera.viewfinder.core)
     implementation(libs.camera.lifecycle)
     implementation(libs.camera.video)
 

core/camera/src/androidTest/java/com/google/jetpackcamera/core/camera/CameraXCameraSystemTest.kt

@@ -32,7 +32,7 @@ import com.google.jetpackcamera.core.camera.postprocess.ImagePostProcessorFeatur
 import com.google.jetpackcamera.core.camera.postprocess.PostProcessModule.Companion.provideImagePostProcessorMap
 import com.google.jetpackcamera.core.camera.utils.APP_REQUIRED_PERMISSIONS
 import com.google.jetpackcamera.core.camera.utils.provideUpdatingSurface
-import com.google.jetpackcamera.core.common.FakeFilePathGenerator
+import com.google.jetpackcamera.core.common.testing.FakeFilePathGenerator
 import com.google.jetpackcamera.model.CaptureMode
 import com.google.jetpackcamera.model.FlashMode
 import com.google.jetpackcamera.model.Illuminant

core/camera/src/main/java/com/google/jetpackcamera/core/camera/CameraSession.kt

@@ -773,7 +773,7 @@ private fun createPreviewUseCase(
 }.build()
     .apply {
         setSurfaceProvider { surfaceRequest ->
-            surfaceRequests.update { surfaceRequest }
+            surfaceRequests.update { PreviewSurfaceRequest.CameraX(surfaceRequest) }
         }
     }
 

core/camera/src/main/java/com/google/jetpackcamera/core/camera/CameraSessionContext.kt

@@ -16,7 +16,6 @@
 package com.google.jetpackcamera.core.camera
 
 import android.content.Context
-import androidx.camera.core.SurfaceRequest
 import androidx.camera.lifecycle.ProcessCameraProvider
 import com.google.jetpackcamera.core.camera.lowlight.LowLightBoostEffectProvider
 import com.google.jetpackcamera.core.common.FilePathGenerator
@@ -41,7 +40,7 @@ internal data class CameraSessionContext(
     val focusMeteringEvents: Channel<CameraEvent.FocusMeteringEvent>,
     val videoCaptureControlEvents: Channel<VideoCaptureControlEvent>,
     val currentCameraState: MutableStateFlow<CameraState>,
-    val surfaceRequests: MutableStateFlow<SurfaceRequest?>,
+    val surfaceRequests: MutableStateFlow<PreviewSurfaceRequest?>,
     val transientSettings: StateFlow<TransientSessionSettings?>,
     val lowLightBoostEffectProvider: LowLightBoostEffectProvider? = null
 )

core/camera/src/main/java/com/google/jetpackcamera/core/camera/CameraSystem.kt

@@ -91,7 +91,12 @@ interface CameraSystem {
 
     fun getCurrentCameraState(): StateFlow<CameraState>
 
-    fun getSurfaceRequest(): StateFlow<SurfaceRequest?>
+    /**
+     * Returns the current [PreviewSurfaceRequest].
+     *
+     * This will be null if no surface is currently requested.
+     */
+    fun getSurfaceRequest(): StateFlow<PreviewSurfaceRequest?>
 
     fun getScreenFlashEvents(): ReceiveChannel<ScreenFlashEvent>
 

core/camera/src/main/java/com/google/jetpackcamera/core/camera/CameraXCameraSystem.kt

@@ -31,7 +31,6 @@ import androidx.camera.core.CameraXConfig
 import androidx.camera.core.DynamicRange as CXDynamicRange
 import androidx.camera.core.ImageCapture
 import androidx.camera.core.ImageCapture.OutputFileOptions
-import androidx.camera.core.SurfaceRequest
 import androidx.camera.core.takePicture
 import androidx.camera.lifecycle.ExperimentalCameraProviderConfiguration
 import androidx.camera.lifecycle.ProcessCameraProvider
@@ -135,9 +134,10 @@ constructor(
     private var currentCameraState = MutableStateFlow(CameraState())
     override fun getCurrentCameraState(): StateFlow<CameraState> = currentCameraState.asStateFlow()
 
-    private val _surfaceRequest = MutableStateFlow<SurfaceRequest?>(null)
+    private val _surfaceRequest = MutableStateFlow<PreviewSurfaceRequest?>(null)
 
-    override fun getSurfaceRequest(): StateFlow<SurfaceRequest?> = _surfaceRequest.asStateFlow()
+    override fun getSurfaceRequest(): StateFlow<PreviewSurfaceRequest?> =
+        _surfaceRequest.asStateFlow()
 
     private val lowLightBoostAvailabilityChecker: LowLightBoostAvailabilityChecker?
     private val lowLightBoostEffectProvider: LowLightBoostEffectProvider?

core/camera/src/main/java/com/google/jetpackcamera/core/camera/FocusMetering.kt

@@ -44,7 +44,9 @@ internal suspend fun CameraSessionContext.processFocusMeteringEvents(
     cameraInfo: CameraInfo,
     cameraControl: CameraControl
 ) {
-    surfaceRequests.flatMapLatest { surfaceRequest ->
+    surfaceRequests.flatMapLatest { previewSurfaceRequest ->
+        val surfaceRequest =
+            (previewSurfaceRequest as? PreviewSurfaceRequest.CameraX)?.surfaceRequest
         surfaceRequest?.let { request ->
             Log.d(
                 TAG,

core/camera/src/main/java/com/google/jetpackcamera/core/camera/PreviewSurfaceRequest.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.jetpackcamera.core.camera
+
+import android.view.Surface
+import androidx.camera.core.SurfaceRequest
+import androidx.camera.viewfinder.core.ViewfinderSurfaceRequest
+import kotlinx.coroutines.CompletableDeferred
+
+/**
+ * A sealed interface representing a request for a preview surface, abstracting the specific
+ * viewfinder implementation required.
+ */
+sealed interface PreviewSurfaceRequest {
+    /**
+     * Wraps a CameraX [SurfaceRequest] for the production CameraXViewfinder.
+     *
+     * @property surfaceRequest The CameraX [SurfaceRequest].
+     */
+    class CameraX(val surfaceRequest: SurfaceRequest) : PreviewSurfaceRequest
+
+    /**
+     * Wraps a [ViewfinderSurfaceRequest] for the standalone Viewfinder composable.
+     *
+     * @property surfaceRequest The standalone [ViewfinderSurfaceRequest].
+     * @property surfaceDeferred A [CompletableDeferred] that will be completed with the [Surface]
+     * once provided by the UI.
+     */
+    class Viewfinder(
+        val surfaceRequest: ViewfinderSurfaceRequest,
+        val surfaceDeferred: CompletableDeferred<Surface> = CompletableDeferred()
+    ) : PreviewSurfaceRequest
+}

core/camera/testing/build.gradle.kts

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+plugins {
+    alias(libs.plugins.android.library)
+    alias(libs.plugins.kotlin.android)
+}
+
+android {
+    namespace = "com.google.jetpackcamera.core.camera.testing"
+    compileSdk = libs.versions.compileSdk.get().toInt()
+
+    defaultConfig {
+        minSdk = libs.versions.minSdk.get().toInt()
+        testOptions.targetSdk = libs.versions.targetSdk.get().toInt()
+        lint.targetSdk = libs.versions.targetSdk.get().toInt()
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    flavorDimensions += "flavor"
+    productFlavors {
+        create("stable") {
+            dimension = "flavor"
+            isDefault = true
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    kotlin {
+        jvmToolchain(17)
+    }
+}
+
+dependencies {
+    implementation(project(":core:camera"))
+    implementation(project(":core:model"))
+    implementation(project(":data:settings"))
+
+    implementation(libs.camera.core)
+    implementation(libs.camera.viewfinder.core)
+    implementation(libs.kotlinx.coroutines.core)
+    // Testing
+    testImplementation(libs.junit)
+    testImplementation(libs.truth)
+    testImplementation(libs.kotlinx.coroutines.test)
+    testImplementation(libs.robolectric)
+}