Add test to verify we haven't regressed on

#28

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

@@ -17,10 +17,13 @@ package com.google.jetpackcamera
 
 import android.content.Context
 import androidx.annotation.StringRes
+import androidx.compose.ui.test.SemanticsMatcher
 import androidx.compose.ui.test.SemanticsNodeInteraction
 import androidx.compose.ui.test.SemanticsNodeInteractionsProvider
 import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.printToString
 import androidx.test.core.app.ApplicationProvider
+import org.junit.AssumptionViolatedException
 
 /**
  * Allows use of testRule.onNodeWithText that uses an integer string resource
@@ -31,3 +34,48 @@ fun SemanticsNodeInteractionsProvider.onNodeWithText(
 ): SemanticsNodeInteraction = onNodeWithText(
     text = ApplicationProvider.getApplicationContext<Context>().getString(strRes)
 )
+
+/**
+ * Assumes that the provided [matcher] is satisfied for this node.
+ *
+ * This is equivalent to [SemanticsNodeInteraction.assert()], but will skip the test rather than
+ * fail the test.
+ *
+ * @param matcher Matcher to verify.
+ * @param messagePrefixOnError Prefix to be put in front of an error that gets thrown in case this
+ * assert fails. This can be helpful in situations where this assert fails as part of a bigger
+ * operation that used this assert as a precondition check.
+ *
+ * @throws AssumptionViolatedException if the matcher does not match or the node can no
+ * longer be found
+ */
+fun SemanticsNodeInteraction.assume(
+    matcher: SemanticsMatcher,
+    messagePrefixOnError: (() -> String)? = null
+): SemanticsNodeInteraction {
+    var errorMessageOnFail = "Failed to assume the following: (${matcher.description})"
+    if (messagePrefixOnError != null) {
+        errorMessageOnFail = messagePrefixOnError() + "\n" + errorMessageOnFail
+    }
+    val node = fetchSemanticsNode(errorMessageOnFail)
+    if (!matcher.matches(node)) {
+        throw AssumptionViolatedException(
+            buildGeneralErrorMessage(errorMessageOnFail, this)
+        )
+    }
+    return this
+}
+
+internal fun buildGeneralErrorMessage(
+    errorMessage: String,
+    nodeInteraction: SemanticsNodeInteraction
+): String {
+    val sb = StringBuilder()
+
+    sb.appendLine(errorMessage)
+
+    sb.appendLine("Semantics of the node:")
+    sb.appendLine(nodeInteraction.printToString())
+
+    return sb.toString()
+}

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

@@ -17,6 +17,7 @@ package com.google.jetpackcamera
 
 import android.app.Activity
 import androidx.compose.ui.test.isDisplayed
+import androidx.compose.ui.test.isEnabled
 import androidx.compose.ui.test.junit4.createEmptyComposeRule
 import androidx.compose.ui.test.onNodeWithTag
 import androidx.compose.ui.test.performClick
@@ -26,6 +27,7 @@ import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.rule.GrantPermissionRule
 import androidx.test.uiautomator.UiDevice
 import com.google.jetpackcamera.feature.preview.ui.CAPTURE_BUTTON
+import com.google.jetpackcamera.feature.preview.ui.FLIP_CAMERA_BUTTON
 import com.google.jetpackcamera.feature.preview.ui.SETTINGS_BUTTON
 import com.google.jetpackcamera.settings.ui.BACK_BUTTON
 import org.junit.Rule
@@ -52,21 +54,17 @@ class NavigationTest {
         }
 
         // Navigate to the settings screen
-        composeTestRule.onNodeWithTag(SETTINGS_BUTTON).apply {
-            assertExists()
-            performClick()
-        }
+        composeTestRule.onNodeWithTag(SETTINGS_BUTTON)
+            .assertExists()
+            .performClick()
 
         // Navigate back using the button
-        composeTestRule.onNodeWithTag(BACK_BUTTON).apply {
-            assertExists()
-            performClick()
-        }
+        composeTestRule.onNodeWithTag(BACK_BUTTON)
+            .assertExists()
+            .performClick()
 
         // Assert we're on PreviewScreen by finding the capture button
-        composeTestRule.onNodeWithTag(CAPTURE_BUTTON).apply {
-            assertExists()
-        }
+        composeTestRule.onNodeWithTag(CAPTURE_BUTTON).assertExists()
 
         // Press the device's back button
         uiDevice.pressBack()
@@ -77,6 +75,35 @@ class NavigationTest {
         ).assertDoesNotExist()
     }
 
+    // Test to ensure we haven't regressed to the cause of
+    // https://github.com/google/jetpack-camera-app/pull/28
+    @Test
+    fun returnFromSettings_afterFlipCamera_returnsToPreview() = runScenarioTest<MainActivity> {
+        // Wait for the capture button to be displayed
+        composeTestRule.waitUntil {
+            composeTestRule.onNodeWithTag(CAPTURE_BUTTON).isDisplayed()
+        }
+
+        // If flipping the camera is available, flip it. Otherwise skip test.
+        composeTestRule.onNodeWithTag(FLIP_CAMERA_BUTTON)
+            .assume(isEnabled()) {
+                "Device does not have multiple cameras to flip between."
+            }.performClick()
+
+        // Navigate to the settings screen
+        composeTestRule.onNodeWithTag(SETTINGS_BUTTON)
+            .assertExists()
+            .performClick()
+
+        // Navigate back using the button
+        composeTestRule.onNodeWithTag(BACK_BUTTON)
+            .assertExists()
+            .performClick()
+
+        // Assert we're on PreviewScreen by finding the capture button
+        composeTestRule.onNodeWithTag(CAPTURE_BUTTON).assertExists()
+    }
+
     private inline fun <reified T : Activity> runScenarioTest(
         crossinline block: ActivityScenario<T>.() -> Unit
     ) {

feature/preview/src/main/java/com/google/jetpackcamera/feature/preview/ui/TestTags.kt

@@ -17,4 +17,4 @@ package com.google.jetpackcamera.feature.preview.ui
 
 const val CAPTURE_BUTTON = "CaptureButton"
 const val SETTINGS_BUTTON = "SettingsButton"
-const val DEFAULT_CAMERA_FACING_SETTING = "SetDefaultCameraFacingSwitch"
+const val FLIP_CAMERA_BUTTON = "FlipCameraButton"