Add tests for MissingChapters function

(cherry picked from commit 8ab7e632936a008d31a87acd335fbd5fb21d818b)

# Conflicts:
#	domain/build.gradle.kts

app/src/main/java/eu/kanade/presentation/manga/MangaScreen.kt

@@ -89,7 +89,7 @@ import exh.ui.metadata.adapters.NHentaiDescription
 import exh.ui.metadata.adapters.PururinDescription
 import exh.ui.metadata.adapters.TsuminoDescription
 import tachiyomi.domain.chapter.model.Chapter
-import tachiyomi.domain.chapter.service.countMissingChapters
+import tachiyomi.domain.chapter.service.missingChaptersCount
 import tachiyomi.domain.manga.model.Manga
 import tachiyomi.domain.source.model.StubSource
 import tachiyomi.presentation.core.components.LazyColumn
@@ -520,7 +520,7 @@ private fun MangaScreenSmallImpl(
                         ChapterHeader(
                             enabled = chapters.fastAll { !it.selected },
                             chapterCount = chapters.size,
-                            missingChapterCount = countMissingChapters(chapters.map { it.chapter.chapterNumber }),
+                            missingChapterCount = chapters.map { it.chapter.chapterNumber }.missingChaptersCount(),
                             onClick = onFilterClicked,
                         )
                     }
@@ -788,7 +788,7 @@ fun MangaScreenLargeImpl(
                                 ChapterHeader(
                                     enabled = chapters.fastAll { !it.selected },
                                     chapterCount = chapters.size,
-                                    missingChapterCount = countMissingChapters(chapters.map { it.chapter.chapterNumber }),
+                                    missingChapterCount = chapters.map { it.chapter.chapterNumber }.missingChaptersCount(),
                                     onClick = onFilterButtonClicked,
                                 )
                             }

app/src/main/java/eu/kanade/presentation/manga/components/ChapterHeader.kt

@@ -14,13 +14,13 @@ import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import eu.kanade.tachiyomi.R
-import tachiyomi.presentation.core.util.secondaryItemAlpha
+import tachiyomi.presentation.core.components.material.SecondaryItemAlpha
 
 @Composable
 fun ChapterHeader(
     enabled: Boolean,
     chapterCount: Int?,
-    missingChapterCount: Int?,
+    missingChapterCount: Int,
     onClick: () -> Unit,
 ) {
     Column(
@@ -48,19 +48,16 @@ fun ChapterHeader(
 }
 
 @Composable
-private fun MissingChaptersWarning(count: Int?) {
-    val text = when {
-        count == null -> stringResource(R.string.missing_chapters_unknown)
-        count > 0 -> pluralStringResource(id = R.plurals.missing_chapters, count = count, count)
-        else -> return
+private fun MissingChaptersWarning(count: Int) {
+    if (count == 0) {
+        return
     }
 
     Text(
-        modifier = Modifier.secondaryItemAlpha(),
-        text = text,
+        text = pluralStringResource(id = R.plurals.missing_chapters, count = count, count),
         maxLines = 1,
         overflow = TextOverflow.Ellipsis,
         style = MaterialTheme.typography.bodySmall,
-        color = MaterialTheme.colorScheme.error,
+        color = MaterialTheme.colorScheme.error.copy(alpha = SecondaryItemAlpha),
     )
 }