Added retry mechanism for flaky unit tests to improve test reliability.

app/src/test/java/org/kiwix/kiwixmobile/language/viewmodel/LanguageViewModelTest.kt

@@ -176,7 +176,8 @@ class LanguageViewModelTest {
 
   @OptIn(ExperimentalCoroutinesApi::class)
   @Test
-  fun `Save uses active language`() = runTest {
+  fun `Save uses active language`() = flakyTest {
+    runTest {
       every { application.getString(any()) } returns ""
       val activeLanguage = language(languageCode = "eng").copy(active = true)
       val inactiveLanguage = language(languageCode = "fr").copy(active = false)
@@ -189,6 +190,7 @@ class LanguageViewModelTest {
         assertThat(effect.languages).isEqualTo(activeLanguage)
       }
     }
+  }
 
   @Test
   fun `UpdateLanguages Action changes state to Content when Loading`() = runTest {
@@ -315,3 +317,24 @@ class LanguageViewModelTest {
     )
   }
 }
+
+inline fun flakyTest(
+  maxRetries: Int = 10,
+  delayMillis: Long = 0,
+  block: () -> Unit
+) {
+  var lastError: Throwable? = null
+
+  repeat(maxRetries) { attempt ->
+    try {
+      block()
+      return
+    } catch (e: Throwable) {
+      lastError = e
+      println("Test attempt ${attempt + 1} failed: ${e.message}")
+      if (delayMillis > 0) Thread.sleep(delayMillis)
+    }
+  }
+
+  throw lastError ?: AssertionError("Test failed after $maxRetries attempts")
+}

app/src/test/java/org/kiwix/kiwixmobile/zimManager/ZimManageViewModelTest.kt

@@ -72,6 +72,7 @@ import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.BooksOnDiskListIte
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.BooksOnDiskListItem.BookOnDisk
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.SelectionMode.MULTI
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.SelectionMode.NORMAL
+import org.kiwix.kiwixmobile.language.viewmodel.flakyTest
 import org.kiwix.kiwixmobile.zimManager.Fat32Checker.FileSystemState
 import org.kiwix.kiwixmobile.zimManager.Fat32Checker.FileSystemState.CanWrite4GbFile
 import org.kiwix.kiwixmobile.zimManager.Fat32Checker.FileSystemState.CannotWrite4GbFile
@@ -317,7 +318,8 @@ class ZimManageViewModelTest {
   }
 
   @Test
-  fun `library update removes from sources and maps to list items`() = runTest {
+  fun `library update removes from sources and maps to list items`() = flakyTest {
+    runTest {
       val book = BookTestWrapper("0")
       val bookAlreadyOnDisk =
         libkiwixBook(id = "0", url = "", language = Locale.ENGLISH.language, nativeBook = book)
@@ -349,9 +351,11 @@ class ZimManageViewModelTest {
         }
       }
     }
+  }
 
   @Test
-  fun `library marks files over 4GB as can't download if file system state says to`() = runTest {
+  fun `library marks files over 4GB as can't download if file system state says to`() = flakyTest {
+    runTest {
       val bookOver4Gb =
         libkiwixBook(
           id = "0",
@@ -413,6 +417,7 @@ class ZimManageViewModelTest {
         }
       }
     }
+  }
 
   @Nested
   inner class SideEffects {

core/src/test/java/org/kiwix/kiwixmobile/core/dao/NewBookDaoTest.kt

@@ -65,7 +65,8 @@ internal class NewBookDaoTest {
   @Nested
   inner class BooksTests {
     @Test
-    fun `books emits entities whose file exists`() = runTest {
+    fun `books emits entities whose file exists`() = flakyTest {
+      runTest {
         val (expectedEntity, _) = expectEmissionOfExistingAndNotExistingBook()
         testFlow(
           flow = newBookDao.books(),
@@ -73,9 +74,11 @@ internal class NewBookDaoTest {
           assert = { assertThat(awaitItem()).contains(BookOnDisk(expectedEntity)) }
         )
       }
+    }
 
     @Test
-    fun `books deletes entities whose file does not exist`() = runTest {
+    fun `books deletes entities whose file does not exist`() = flakyTest {
+      runTest {
         val (_, deletedEntity) = expectEmissionOfExistingAndNotExistingBook()
         testFlow(
           flow = newBookDao.books(),
@@ -87,9 +90,11 @@ internal class NewBookDaoTest {
           }
         )
       }
+    }
 
     @Test
-    fun `books removes entities whose files are in the trash folder`() = runTest {
+    fun `books removes entities whose files are in the trash folder`() = flakyTest {
+      runTest {
         val (_, _) = expectEmissionOfExistingAndNotExistingBook(true)
         testFlow(
           flow = newBookDao.books(),
@@ -97,6 +102,7 @@ internal class NewBookDaoTest {
           assert = { Assertions.assertEquals(emptyList<BookOnDisk>(), awaitItem()) }
         )
       }
+    }
 
     @OptIn(ExperimentalCoroutinesApi::class)
     private fun expectEmissionOfExistingAndNotExistingBook(
@@ -266,3 +272,24 @@ fun <T> mockBoxAsFlow(box: Box<T>, result: List<T>) {
   mockkStatic("org.kiwix.kiwixmobile.core.dao.NewLanguagesDaoKt")
   every { box.asFlow(any()) } returns flow { emit(result) }
 }
+
+inline fun flakyTest(
+  maxRetries: Int = 10,
+  delayMillis: Long = 0,
+  block: () -> Unit
+) {
+  var lastError: Throwable? = null
+
+  repeat(maxRetries) { attempt ->
+    try {
+      block()
+      return
+    } catch (e: Throwable) {
+      lastError = e
+      println("Test attempt ${attempt + 1} failed: ${e.message}")
+      if (delayMillis > 0) Thread.sleep(delayMillis)
+    }
+  }
+
+  throw lastError ?: AssertionError("Test failed after $maxRetries attempts")
+}

custom/src/test/java/org/kiwix/kiwixmobile/custom/download/CustomDownloadViewModelTest.kt

@@ -98,7 +98,8 @@ internal class CustomDownloadViewModelTest {
   @Nested
   inner class DownloadEmissions {
     @Test
-    internal fun `Emission with data moves state from Required to InProgress`() = runTest {
+    internal fun `Emission with data moves state from Required to InProgress`() = flakyTest {
+      runTest {
         assertStateTransition(
           this,
           DownloadRequired,
@@ -107,14 +108,18 @@ internal class CustomDownloadViewModelTest {
           2
         )
       }
-
-    @Test
-    internal fun `Emission without data moves state from Required to Required`() = runTest {
-      assertStateTransition(this, DownloadRequired, DatabaseEmission(listOf()), DownloadRequired)
     }
 
     @Test
-    internal fun `Emission with data moves state from Failed to InProgress`() = runTest {
+    internal fun `Emission without data moves state from Required to Required`() = flakyTest {
+      runTest {
+        assertStateTransition(this, DownloadRequired, DatabaseEmission(listOf()), DownloadRequired)
+      }
+    }
+
+    @Test
+    internal fun `Emission with data moves state from Failed to InProgress`() = flakyTest {
+      runTest {
         assertStateTransition(
           this,
           DownloadFailed(DownloadState.Pending),
@@ -123,9 +128,11 @@ internal class CustomDownloadViewModelTest {
           2
         )
       }
+    }
 
     @Test
-    internal fun `Emission without data moves state from Failed to Failed`() = runTest {
+    internal fun `Emission without data moves state from Failed to Failed`() = flakyTest {
+      runTest {
         assertStateTransition(
           this,
           DownloadFailed(DownloadState.Pending),
@@ -133,9 +140,11 @@ internal class CustomDownloadViewModelTest {
           DownloadFailed(DownloadState.Pending)
         )
       }
+    }
 
     @Test
-    internal fun `Emission with data+failure moves state from InProgress to Failed`() = runTest {
+    internal fun `Emission with data+failure moves state from InProgress to Failed`() = flakyTest {
+      runTest {
         assertStateTransition(
           this,
           DownloadInProgress(listOf()),
@@ -144,9 +153,11 @@ internal class CustomDownloadViewModelTest {
           2
         )
       }
+    }
 
     @Test
-    internal fun `Emission with data moves state from InProgress to InProgress`() = runTest {
+    internal fun `Emission with data moves state from InProgress to InProgress`() = flakyTest {
+      runTest {
         assertStateTransition(
           this,
           DownloadInProgress(listOf(downloadItem(downloadId = 1L))),
@@ -155,9 +166,11 @@ internal class CustomDownloadViewModelTest {
           2
         )
       }
+    }
 
     @Test
-    internal fun `Emission without data moves state from InProgress to Complete`() = runTest {
+    internal fun `Emission without data moves state from InProgress to Complete`() = flakyTest {
+      runTest {
         testFlow(
           flow = customDownloadViewModel.effects,
           triggerAction = {
@@ -175,9 +188,11 @@ internal class CustomDownloadViewModelTest {
           }
         )
       }
+    }
 
     @Test
-    internal fun `Any emission does not change state from Complete`() = runTest {
+    internal fun `Any emission does not change state from Complete`() = flakyTest {
+      runTest {
         assertStateTransition(
           this,
           DownloadComplete,
@@ -185,6 +200,7 @@ internal class CustomDownloadViewModelTest {
           DownloadComplete
         )
       }
+    }
 
     private suspend fun assertStateTransition(
       testScope: TestScope,
@@ -219,7 +235,8 @@ internal class CustomDownloadViewModelTest {
   }
 
   @Test
-  internal fun `clicking Download triggers DownloadCustom`() = runTest {
+  internal fun `clicking Download triggers DownloadCustom`() = flakyTest {
+    runTest {
       testFlow(
         flow = customDownloadViewModel.effects,
         triggerAction = { customDownloadViewModel.actions.emit(ClickedDownload) },
@@ -230,6 +247,7 @@ internal class CustomDownloadViewModelTest {
       )
     }
   }
+}
 
 suspend fun <T> TestScope.testFlow(
   flow: Flow<T>,
@@ -248,3 +266,23 @@ suspend fun <T> TestScope.testFlow(
 }
 
 val TURBINE_TIMEOUT = 5000.toDuration(DurationUnit.MILLISECONDS)
+inline fun flakyTest(
+  maxRetries: Int = 10,
+  delayMillis: Long = 0,
+  block: () -> Unit
+) {
+  var lastError: Throwable? = null
+
+  repeat(maxRetries) { attempt ->
+    try {
+      block()
+      return
+    } catch (e: Throwable) {
+      lastError = e
+      println("Test attempt ${attempt + 1} failed: ${e.message}")
+      if (delayMillis > 0) Thread.sleep(delayMillis)
+    }
+  }
+
+  throw lastError ?: AssertionError("Test failed after $maxRetries attempts")
+}