test(android): screenshot tests for every screen

Roborazzi draws Library (phone, tablet, font scale 1.5, empty), a title,
Shares, Settings and Downloads from fixed records under Robolectric, and
build-android.sh check compares them with the committed images in
app/src/test/screenshots. The redesign changes every screen; a layout
regression now fails the gate and shows up in review as a changed image.

android/app/build.gradle.kts

@@ -6,6 +6,7 @@ plugins {
     alias(libs.plugins.kotlin.android)
     alias(libs.plugins.kotlin.compose)
     alias(libs.plugins.ktlint)
+    alias(libs.plugins.roborazzi)
 }
 
 val repositoryRoot = rootProject.projectDir.parentFile
@@ -272,6 +273,11 @@ dependencies {
     testImplementation(libs.robolectric)
     testImplementation(libs.androidx.test.core)
     testImplementation(libs.androidx.work.testing)
+    testImplementation(platform(libs.androidx.compose.bom))
+    testImplementation(libs.androidx.compose.ui.test.junit4)
+    testImplementation(libs.roborazzi)
+    testImplementation(libs.roborazzi.compose)
+    testImplementation(libs.roborazzi.junit.rule)
 
     androidTestImplementation(libs.androidx.test.junit)
     androidTestImplementation(libs.androidx.test.core)
@@ -295,6 +301,13 @@ ktlint {
     }
 }
 
+// Screenshot baselines live beside the tests that draw them, so a change to how
+// a screen looks shows up in review as a changed image. `recordRoborazziDebug`
+// rewrites them; `verifyRoborazziDebug` fails on any difference.
+roborazzi {
+    outputDir.set(file("src/test/screenshots"))
+}
+
 // The generated UniFFI directory is a main source dir, so ktlint reads it even
 // though the filter above drops every file in it. Without this, Gradle refuses
 // the build for an undeclared dependency between the two tasks.

android/app/src/test/java/io/narl/protonstream/ui/ScreenshotTest.kt

@@ -0,0 +1,180 @@
+package io.narl.protonstream.ui
+
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.ui.test.junit4.createComposeRule
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.test.onRoot
+import androidx.compose.ui.unit.Density
+import androidx.test.core.app.ApplicationProvider
+import androidx.work.testing.WorkManagerTestInitHelper
+import com.github.takahirom.roborazzi.RobolectricDeviceQualifiers
+import com.github.takahirom.roborazzi.captureRoboImage
+import io.narl.protonstream.ui.theme.ProtonStreamTheme
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import org.robolectric.annotation.GraphicsMode
+import uniffi.pstr_android.EpisodeRecord
+import uniffi.pstr_android.SeasonRecord
+import uniffi.pstr_android.ShareRecord
+import uniffi.pstr_android.StorageUsageRecord
+import uniffi.pstr_android.TitleRecord
+import uniffi.pstr_android.TitleType
+
+/**
+ * Every screen, drawn from fixed records, against a committed image.
+ *
+ * The screens are about to be redesigned one by one, and a layout regression —
+ * a row that wraps, a button pushed off the edge — compiles and passes every
+ * other test. Here it is a changed PNG in review. No artwork is loaded: the
+ * bridge is not available on the host, so every tile shows its placeholder,
+ * which is also what a title without metadata looks like on a phone.
+ */
+@RunWith(RobolectricTestRunner::class)
+@GraphicsMode(GraphicsMode.Mode.NATIVE)
+@Config(qualifiers = RobolectricDeviceQualifiers.Pixel7)
+class ScreenshotTest {
+    @get:Rule val compose = createComposeRule()
+
+    @Before
+    fun setUp() {
+        WorkManagerTestInitHelper.initializeTestWorkManager(ApplicationProvider.getApplicationContext())
+    }
+
+    private fun capture(name: String, content: @Composable () -> Unit) {
+        compose.setContent {
+            ProtonStreamTheme {
+                Surface(color = MaterialTheme.colorScheme.background) { content() }
+            }
+        }
+        compose.onRoot().captureRoboImage("src/test/screenshots/$name.png")
+    }
+
+    @Test
+    fun `the library on a phone`() = capture("library-phone") {
+        LibraryScreen(LIBRARY, {}, { _, _ -> }, {}, PaddingValues())
+    }
+
+    @Test
+    @Config(qualifiers = RobolectricDeviceQualifiers.MediumTablet)
+    fun `the library on a tablet`() = capture("library-tablet") {
+        LibraryScreen(LIBRARY, {}, { _, _ -> }, {}, PaddingValues())
+    }
+
+    @Test
+    fun `the library at a large font scale`() = capture("library-phone-large-font") {
+        // Robolectric has no font-scale qualifier; the density is what Compose
+        // reads it from, so the scale is set there.
+        val density = LocalDensity.current
+        CompositionLocalProvider(LocalDensity provides Density(density.density, fontScale = 1.5f)) {
+            LibraryScreen(LIBRARY, {}, { _, _ -> }, {}, PaddingValues())
+        }
+    }
+
+    @Test
+    fun `an empty library`() = capture("library-empty") {
+        LibraryScreen(AppUiState(loading = false), {}, { _, _ -> }, {}, PaddingValues())
+    }
+
+    @Test
+    fun `a title with seasons`() = capture("title-phone") {
+        TitleScreen(SERIES, true, { _, _ -> }, {}, {}, {}, { _, _ -> }, PaddingValues())
+    }
+
+    @Test
+    fun `the shares page`() = capture("shares-phone") {
+        SharesScreen(LIBRARY.shares, { _, _, _ -> }, { _, _, _ -> }, {}, {}, null, {}, PaddingValues())
+    }
+
+    @Test
+    fun `the settings page`() = capture("settings-phone") {
+        SettingsScreen(LIBRARY, { _, _, _, _ -> }, {}, {}, {}, PaddingValues())
+    }
+
+    @Test
+    fun `the downloads page with nothing offline`() = capture("downloads-empty") {
+        DownloadsScreen(LIBRARY, {}, {}, {}, {}, PaddingValues())
+    }
+
+    private companion object {
+        fun episode(season: UInt, number: UInt, watched: Boolean = false, progress: Double? = null) = EpisodeRecord(
+            shareId = "share",
+            volumeId = "volume",
+            linkId = "s${season}e$number",
+            name = "[Group] Oshi no Ko - S%02dE%02d.mkv".format(season.toInt(), number.toInt()),
+            label = "S%02dE%02d".format(season.toInt(), number.toInt()),
+            detail = "1.2 GiB",
+            season = season,
+            number = number,
+            size = 1_300_000_000uL,
+            progress = progress,
+            resumeAt = progress?.let { it * 1440 },
+            watched = watched,
+            offline = false,
+            providerName = if (number == 1u) "Mother and Children" else null,
+            providerOverview = null,
+            stillUrl = null,
+            airDate = null,
+            lastPlayed = if (progress != null) 1_790_000_000L else 0L,
+        )
+
+        fun title(key: String, name: String, seasons: List<SeasonRecord>, overview: String? = null) = TitleRecord(
+            key = key,
+            name = name,
+            year = 2023u,
+            kind = TitleType.SERIES,
+            watchedCount = seasons.sumOf { s -> s.episodes.count { it.watched } }.toULong(),
+            episodeCount = seasons.sumOf { it.episodes.size }.toULong(),
+            canonicalName = null,
+            originalName = null,
+            overview = overview,
+            metadataProvider = null,
+            metadataId = null,
+            metadataYear = null,
+            metadataKind = null,
+            posterUrl = null,
+            backdropUrl = null,
+            rating = 8.4,
+            genres = listOf("Drama", "Mystery"),
+            providerEpisodeCount = null,
+            externalUrl = null,
+            manualMatch = false,
+            seasons = seasons,
+        )
+
+        val SERIES = title(
+            "oshi-no-ko",
+            "Oshi no Ko",
+            listOf(
+                SeasonRecord(1u, "Season 1", (1u..4u).map { episode(1u, it, watched = it < 3u) }),
+                SeasonRecord(2u, "Season 2", (1u..3u).map { episode(2u, it, progress = if (it == 1u) 0.4 else null) }),
+            ),
+            overview = "A doctor in a countryside clinic is reborn as the child of the idol he followed.",
+        )
+
+        val FILM = title("akira", "Akira", listOf(SeasonRecord(null, "Film", listOf(episode(1u, 1u)))))
+            .copy(kind = TitleType.FILM, year = 1988u)
+
+        val LIBRARY = AppUiState(
+            loading = false,
+            titles = listOf(
+                FILM,
+                SERIES,
+                title("ano-hana", "Ano Hi Mita Hana no Namae o Bokutachi wa Mada Shiranai.", listOf(SeasonRecord(1u, "Season 1", (1u..11u).map { episode(1u, it) }))),
+                title("bleach", "Bleach", listOf(SeasonRecord(1u, "Season 1", (1u..2u).map { episode(1u, it) }))),
+            ),
+            shares = listOf(
+                ShareRecord("anime", "anime", true),
+                ShareRecord("films", "films", false),
+            ),
+            storage = StorageUsageRecord(6_400_000_000uL, 3uL, 0uL, 1_100_000_000uL),
+        )
+    }
+}