Added test cases for custom apps to cover this scenario and prevent future errors.

* Refactored some deprecated methods used in test cases.

custom/src/androidTest/java/org/kiwix/kiwixmobile/custom/search/SearchFragmentTestForCustomApp.kt

@@ -90,8 +90,10 @@ class SearchFragmentTestForCustomApp {
   private lateinit var downloadingZimFile: File
   private lateinit var activityScenario: ActivityScenario<CustomMainActivity>
 
-  private val rayCharlesZimFileUrl =
+  private val scientificAllianceZIMUrl =
     "https://download.kiwix.org/zim/zimit/scientific-alliance.obscurative.ru_ru_all_2024-06.zim"
+  private val rayCharlesZIMFileUrl =
+    "https://dev.kiwix.org/kiwix-android/test/wikipedia_en_ray_charles_maxi_2023-12.zim"
 
   @Before
   fun waitForIdle() {
@@ -258,6 +260,44 @@ class SearchFragmentTestForCustomApp {
     }
   }
 
+  @Test
+  fun testPreviouslyLoadedArticleLoadsAgainWhenSwitchingToAnotherScreen() {
+    activityScenario.onActivity {
+      customMainActivity = it
+    }
+    // test with a large ZIM file to properly test the scenario
+    downloadingZimFile = getDownloadingZimFileFromDataFolder()
+    getOkkHttpClientForTesting().newCall(downloadRequest(rayCharlesZIMFileUrl)).execute()
+      .use { response ->
+        if (response.isSuccessful) {
+          response.body?.let { responseBody ->
+            writeZimFileData(responseBody, downloadingZimFile)
+          }
+        } else {
+          throw RuntimeException(
+            "Download Failed. Error: ${response.message}\n" +
+              " Status Code: ${response.code}"
+          )
+        }
+      }
+    UiThreadStatement.runOnUiThread {
+      customMainActivity.navigate(customMainActivity.readerFragmentResId)
+    }
+    openZimFileInReader(zimFile = downloadingZimFile)
+    search {
+      // click on home button to load the main page of ZIM file.
+      clickOnHomeButton()
+      // click on an article to load the other page.
+      clickOnAFoolForYouArticle()
+      assertAFoolForYouArticleLoaded()
+      // open note screen.
+      openNoteFragment()
+      pressBack()
+      // after came back check the previously loaded article is still showing or not.
+      assertAFoolForYouArticleLoaded()
+    }
+  }
+
   private fun openSearchWithQuery(query: String = "") {
     UiThreadStatement.runOnUiThread {
       customMainActivity.openSearch(searchString = query)
@@ -270,7 +310,10 @@ class SearchFragmentTestForCustomApp {
     }
   }
 
-  private fun openZimFileInReader(assetFileDescriptor: AssetFileDescriptor) {
+  private fun openZimFileInReader(
+    assetFileDescriptor: AssetFileDescriptor? = null,
+    zimFile: File? = null
+  ) {
     UiThreadStatement.runOnUiThread {
       val navHostFragment: NavHostFragment =
         customMainActivity.supportFragmentManager
@@ -280,10 +323,17 @@ class SearchFragmentTestForCustomApp {
       val customReaderFragment =
         navHostFragment.childFragmentManager.fragments[0] as CustomReaderFragment
       runBlocking {
-        customReaderFragment.openZimFile(
-          ZimReaderSource(null, null, listOf(assetFileDescriptor)),
-          true
-        )
+        assetFileDescriptor?.let {
+          customReaderFragment.openZimFile(
+            ZimReaderSource(assetFileDescriptorList = listOf(assetFileDescriptor)),
+            true
+          )
+        } ?: run {
+          customReaderFragment.openZimFile(
+            ZimReaderSource(zimFile),
+            true
+          )
+        }
       }
     }
   }
@@ -318,9 +368,9 @@ class SearchFragmentTestForCustomApp {
     }
   }
 
-  private fun downloadRequest() =
+  private fun downloadRequest(zimUrl: String = scientificAllianceZIMUrl) =
     Request.Builder()
-      .url(URI.create(rayCharlesZimFileUrl).toURL())
+      .url(URI.create(zimUrl).toURL())
       .build()
 
   private fun getDownloadingZimFile(): File {
@@ -330,6 +380,13 @@ class SearchFragmentTestForCustomApp {
     return zimFile
   }
 
+  private fun getDownloadingZimFileFromDataFolder(): File {
+    val zimFile = File(context.getExternalFilesDirs(null)[0], "ray_charles.zim")
+    if (zimFile.exists()) zimFile.delete()
+    zimFile.createNewFile()
+    return zimFile
+  }
+
   @Singleton
   private fun getOkkHttpClientForTesting(): OkHttpClient =
     OkHttpClient().newBuilder()

custom/src/androidTest/java/org/kiwix/kiwixmobile/custom/search/SearchRobot.kt

@@ -19,19 +19,31 @@
 package org.kiwix.kiwixmobile.custom.search
 
 import android.view.KeyEvent
+import androidx.core.view.GravityCompat
 import androidx.recyclerview.widget.RecyclerView
 import androidx.test.espresso.Espresso
+import androidx.test.espresso.Espresso.onView
 import androidx.test.espresso.action.ViewActions
+import androidx.test.espresso.action.ViewActions.click
 import androidx.test.espresso.assertion.ViewAssertions
 import androidx.test.espresso.contrib.RecyclerViewActions
 import androidx.test.espresso.matcher.ViewMatchers
+import androidx.test.espresso.matcher.ViewMatchers.withText
+import androidx.test.espresso.web.assertion.WebViewAssertions.webMatches
 import androidx.test.espresso.web.sugar.Web
+import androidx.test.espresso.web.sugar.Web.onWebView
 import androidx.test.espresso.web.webdriver.DriverAtoms
+import androidx.test.espresso.web.webdriver.DriverAtoms.findElement
+import androidx.test.espresso.web.webdriver.DriverAtoms.getText
+import androidx.test.espresso.web.webdriver.DriverAtoms.webClick
 import androidx.test.espresso.web.webdriver.Locator
 import androidx.test.uiautomator.UiDevice
+import com.adevinta.android.barista.interaction.BaristaDrawerInteractions.openDrawerWithGravity
 import com.adevinta.android.barista.interaction.BaristaSleepInteractions
 import com.adevinta.android.barista.internal.matcher.HelperMatchers
+import org.hamcrest.CoreMatchers.containsString
 import org.kiwix.kiwixmobile.core.R
+import org.kiwix.kiwixmobile.custom.R.id
 import org.kiwix.kiwixmobile.custom.testutils.TestUtils
 import org.kiwix.kiwixmobile.custom.testutils.TestUtils.testFlakyView
 
@@ -118,4 +130,43 @@ class SearchRobot {
         )
     })
   }
+
+  fun clickOnHomeButton() {
+    testFlakyView({
+      Espresso.onView(ViewMatchers.withId(R.id.bottom_toolbar_home))
+        .perform(ViewActions.click())
+    })
+  }
+
+  fun clickOnAFoolForYouArticle() {
+    BaristaSleepInteractions.sleep(TestUtils.TEST_PAUSE_MS.toLong())
+    testFlakyView({
+      onWebView()
+        .withElement(
+          findElement(
+            Locator.XPATH,
+            "//*[contains(text(), 'A Fool for You')]"
+          )
+        ).perform(webClick())
+    })
+  }
+
+  fun assertAFoolForYouArticleLoaded() {
+    BaristaSleepInteractions.sleep(TestUtils.TEST_PAUSE_MS.toLong())
+    testFlakyView({
+      onWebView()
+        .withElement(
+          findElement(
+            Locator.XPATH,
+            "//*[contains(text(), '\"A Fool for You\"')]"
+          )
+        ).check(webMatches(getText(), containsString("\"A Fool for You\"")))
+    })
+  }
+
+  fun openNoteFragment() {
+    BaristaSleepInteractions.sleep(TestUtils.TEST_PAUSE_MS.toLong())
+    openDrawerWithGravity(id.custom_drawer_container, GravityCompat.START)
+    testFlakyView({ onView(withText(R.string.pref_notes)).perform(click()) })
+  }
 }

custom/src/androidTest/java/org/kiwix/kiwixmobile/custom/testutils/TestUtils.kt

@@ -21,7 +21,6 @@ package org.kiwix.kiwixmobile.custom.testutils
 import android.content.Context
 import android.content.ContextWrapper
 import android.content.Intent
-import androidx.core.content.ContextCompat
 import androidx.test.uiautomator.By
 import androidx.test.uiautomator.UiDevice
 import androidx.test.uiautomator.UiObject
@@ -32,6 +31,7 @@ import java.io.File
 object TestUtils {
   private const val TAG = "TESTUTILS"
   var TEST_PAUSE_MS_FOR_SEARCH_TEST = 1000
+  var TEST_PAUSE_MS = 3000
 
   @JvmStatic
   fun isSystemUINotRespondingDialogVisible(uiDevice: UiDevice) =
@@ -92,7 +92,7 @@ object TestUtils {
 
   @JvmStatic
   fun deleteTemporaryFilesOfTestCases(context: Context) {
-    ContextCompat.getExternalFilesDirs(context, null).filterNotNull()
+    context.getExternalFilesDirs(null).filterNotNull()
       .map(::deleteAllFilesInDirectory)
     ContextWrapper(context).externalMediaDirs.filterNotNull()
       .map(::deleteAllFilesInDirectory)