Fix cross-test interference in SingleLensModeTest

app/build.gradle.kts

@@ -131,6 +131,7 @@ dependencies {
     androidTestImplementation(libs.androidx.espresso.core)
     androidTestImplementation(libs.androidx.rules)
     androidTestImplementation(libs.androidx.uiautomator)
+    androidTestImplementation(libs.camera.lifecycle) // to reset CameraX between tests
     androidTestImplementation(libs.truth)
     androidTestImplementation(project(":ui:components:capture"))
     androidTestUtil(libs.androidx.orchestrator)

app/src/androidTest/java/com/google/jetpackcamera/SingleLensModeTest.kt

@@ -24,6 +24,7 @@ import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
 import com.google.common.truth.TruthJUnit.assume
 import com.google.jetpackcamera.ui.components.capture.FLIP_CAMERA_BUTTON
+import com.google.jetpackcamera.utils.CameraXResetRule
 import com.google.jetpackcamera.utils.TEST_REQUIRED_PERMISSIONS
 import com.google.jetpackcamera.utils.isEmulatorWithFakeFrontCamera
 import com.google.jetpackcamera.utils.runMainActivityScenarioTest
@@ -35,6 +36,9 @@ import org.junit.runners.Parameterized
 
 @RunWith(Parameterized::class)
 class SingleLensModeTest(private val lensFacing: String) {
+    @get:Rule
+    val cameraXResetRule = CameraXResetRule()
+
     @get:Rule
     val permissionsRule: GrantPermissionRule =
         GrantPermissionRule.grant(*(TEST_REQUIRED_PERMISSIONS).toTypedArray())

app/src/androidTest/java/com/google/jetpackcamera/utils/AppTestUtil.kt

@@ -24,13 +24,53 @@ import android.os.Environment
 import android.provider.BaseColumns
 import android.provider.MediaStore
 import android.util.Log
+import androidx.camera.lifecycle.ProcessCameraProvider
+import androidx.test.platform.app.InstrumentationRegistry
 import java.io.File
+import java.util.concurrent.TimeUnit
 import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.transform
+import org.junit.rules.TestRule
+import org.junit.runner.Description
+import org.junit.runners.model.Statement
 
 private const val TAG = "AppTestUtil"
+private const val CAMERAX_RESET_TIMEOUT_SECONDS = 10L
+
+/**
+ * A [TestRule] that resets CameraX before each test.
+ *
+ * This is useful for tests that need to configure CameraX (e.g. using
+ * [ProcessCameraProvider.configureInstance]), which can only be done once per process.
+ */
+class CameraXResetRule : TestRule {
+    override fun apply(base: Statement, description: Description): Statement {
+        return object : Statement() {
+            override fun evaluate() {
+                val context = InstrumentationRegistry.getInstrumentation().targetContext
+                initializeAndShutdown(context)
+                try {
+                    base.evaluate()
+                } finally {
+                    initializeAndShutdown(context)
+                }
+            }
+        }
+    }
+
+    private fun initializeAndShutdown(context: android.content.Context) {
+        try {
+            ProcessCameraProvider.getInstance(context)
+                .get(CAMERAX_RESET_TIMEOUT_SECONDS, TimeUnit.SECONDS)
+                .shutdownAsync()
+                .get(CAMERAX_RESET_TIMEOUT_SECONDS, TimeUnit.SECONDS)
+        } catch (e: Exception) {
+            Log.w(TAG, "Failed to shutdown CameraX", e)
+        }
+    }
+}
 
 internal val APP_REQUIRED_PERMISSIONS: List<String> = buildList {
     add(android.Manifest.permission.CAMERA)