New snapshot test for LazyList loading and unloading (#2265)

* New snapshot test for LazyList loading and unloading

This is in the wrong module as I intend to reuse the test infrastructure
in redwood-layout-uiview to test the iOS implementation.

* Test UIViewLazyList

* Delay snapshots one frame

* record: false

* Copy-paste snapshot testing infrastructure for lazylist

Rather than using the wrong module, or introducing build infrastructure
to abstract it up.

.github/workflows/build.yaml

@@ -85,6 +85,8 @@ jobs:
 
       - run: xcodebuild -project redwood-layout-uiview/RedwoodLayoutUIViewTests.xcodeproj -scheme RedwoodLayoutUIViewTests -destination 'platform=iOS Simulator,name=iPhone 15,OS=17.5' test
 
+      - run: xcodebuild -project redwood-lazylayout-uiview/RedwoodLazylayoutUIViewTests.xcodeproj -scheme RedwoodLazylayoutUIViewTests -destination 'platform=iOS Simulator,name=iPhone 15,OS=17.5' test
+
       - uses: actions/upload-artifact@v4
         if: ${{ always() }}
         with:

redwood-layout-uiview/RedwoodLayoutUIViewTests/SnapshotTestingCallback.swift

@@ -11,9 +11,9 @@ final class SnapshotTestingCallback : UIViewSnapshotCallback {
         self.fileName = fileName
     }
 
-    func verifySnapshot(view: UIView, name: String?) {
+    func verifySnapshot(view: UIView, name: String?, delay: TimeInterval = 0.0) {
         // Set `record` to true to generate new snapshots. Be sure to revert that before committing!
         // Note that tests always fail when `record` is true.
-        assertSnapshot(of: view, as: .image, named: name, record: false, file: fileName, testName: testName)
+        assertSnapshot(of: view, as: .wait(for: delay, on: .image), named: name, record: false, file: fileName, testName: testName)
     }
 }

redwood-layout-uiview/src/commonTest/kotlin/app/cash/redwood/layout/uiview/UIViewSnapshotCallback.kt

@@ -18,5 +18,5 @@ package app.cash.redwood.layout.uiview
 import platform.UIKit.UIView
 
 interface UIViewSnapshotCallback {
-  fun verifySnapshot(view: UIView, name: String?)
+  fun verifySnapshot(view: UIView, name: String?, delay: Double = 0.0)
 }

redwood-lazylayout-shared-test/build.gradle

@@ -0,0 +1,28 @@
+import static app.cash.redwood.buildsupport.TargetGroup.ToolkitAllWithoutAndroid
+
+redwoodBuild {
+  targets(ToolkitAllWithoutAndroid)
+}
+
+kotlin {
+  sourceSets {
+    commonMain {
+      dependencies {
+        api projects.redwoodLazylayoutApi
+        api projects.redwoodLazylayoutWidget
+        api projects.redwoodRuntime
+        api projects.redwoodWidget
+        api projects.redwoodYoga
+        api libs.kotlin.test
+      }
+    }
+    jvmMain {
+      dependencies {
+        // The kotlin.test library provides JVM variants for multiple testing frameworks. When used
+        // as a test dependency this selection is transparent. But since we are publishing a library
+        // we need to select one ourselves at compilation time.
+        api libs.kotlin.test.junit
+      }
+    }
+  }
+}

redwood-lazylayout-shared-test/src/commonMain/kotlin/app/cash/redwood/lazylayout/AbstractLazyListTest.kt

@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.redwood.lazylayout
+
+import app.cash.redwood.Modifier
+import app.cash.redwood.layout.api.Constraint
+import app.cash.redwood.layout.api.CrossAxisAlignment
+import app.cash.redwood.lazylayout.api.ScrollItemIndex
+import app.cash.redwood.lazylayout.widget.LazyList
+import app.cash.redwood.ui.Margin
+import app.cash.redwood.ui.dp
+import app.cash.redwood.widget.ChangeListener
+import app.cash.redwood.widget.Widget
+import kotlin.test.Test
+
+abstract class AbstractLazyListTest<T : Any> {
+  abstract fun text(): Text<T>
+
+  private fun coloredText(
+    modifier: Modifier = Modifier,
+    text: String,
+    backgroundColor: Int = Green,
+  ) = text().apply {
+    this.modifier = modifier
+    text(text)
+    bgColor(backgroundColor)
+  }
+
+  abstract fun lazyList(
+    backgroundColor: Int = argb(51, 0, 0, 255),
+  ): LazyList<T>
+
+  private fun defaultLazyList(): LazyList<T> {
+    val result = lazyList()
+    for (i in 0 until 10) {
+      result.placeholder.insert(i, coloredText(text = "..."))
+    }
+    result.isVertical(true)
+    result.itemsBefore(0)
+    result.itemsAfter(0)
+    result.width(Constraint.Fill)
+    result.height(Constraint.Fill)
+    result.margin(Margin(all = 0.dp))
+    result.crossAxisAlignment(CrossAxisAlignment.Stretch)
+    result.scrollItemIndex(ScrollItemIndex(id = 0, index = 0))
+    return result
+  }
+
+  abstract fun verifySnapshot(
+    container: Widget<T>,
+    name: String? = null,
+  )
+
+  @Test fun testHappyPath() {
+    val lazyList = defaultLazyList()
+
+    for ((index, value) in movies.take(5).withIndex()) {
+      lazyList.items.insert(index, coloredText(text = value))
+    }
+    (lazyList as? ChangeListener)?.onEndChanges()
+
+    verifySnapshot(lazyList)
+  }
+
+  @Test fun testPlaceholderToLoadedAndLoadedToPlaceholder() {
+    val lazyList = defaultLazyList()
+
+    (lazyList as? ChangeListener)?.onEndChanges()
+    verifySnapshot(lazyList, "0 empty")
+
+    lazyList.itemsBefore(0)
+    lazyList.itemsAfter(10)
+    (lazyList as? ChangeListener)?.onEndChanges()
+    verifySnapshot(lazyList, "1 placeholders")
+
+    lazyList.itemsBefore(0)
+    lazyList.itemsAfter(0)
+    for ((index, value) in movies.take(10).withIndex()) {
+      lazyList.items.insert(index, coloredText(text = value))
+    }
+    (lazyList as? ChangeListener)?.onEndChanges()
+    verifySnapshot(lazyList, "2 loaded")
+
+    lazyList.itemsBefore(0)
+    lazyList.itemsAfter(10)
+    lazyList.items.remove(0, 10)
+    (lazyList as? ChangeListener)?.onEndChanges()
+    verifySnapshot(lazyList, "3 placeholders")
+
+    lazyList.itemsBefore(0)
+    lazyList.itemsAfter(0)
+    (lazyList as? ChangeListener)?.onEndChanges()
+    verifySnapshot(lazyList, "4 empty")
+  }
+
+  @Test fun testPlaceholdersExhausted() {
+    val lazyList = defaultLazyList()
+
+    lazyList.itemsBefore(11)
+    for ((index, value) in movies.take(1).withIndex()) {
+      lazyList.items.insert(index, coloredText(text = value))
+    }
+    (lazyList as? ChangeListener)?.onEndChanges()
+    verifySnapshot(lazyList)
+  }
+}
+
+private val movies = listOf(
+  "The Godfather",
+  "The Dark Knight",
+  "12 Angry Men",
+  "Schindler's List",
+  "Pulp Fiction",
+  "Forrest Gump",
+  "Fight Club",
+  "Inception",
+  "The Matrix",
+  "Goodfellas",
+  "Se7en",
+  "Seven Samurai",
+)

redwood-lazylayout-shared-test/src/commonMain/kotlin/app/cash/redwood/lazylayout/utils.common.kt

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@file:Suppress("ktlint:standard:property-naming")
+
+package app.cash.redwood.lazylayout
+
+import app.cash.redwood.widget.Widget
+
+const val Green: Int = 0xff00ff00.toInt()
+
+fun argb(
+  alpha: Int,
+  red: Int,
+  green: Int,
+  blue: Int,
+): Int {
+  return (alpha shl 24) or (red shl 16) or (green shl 8) or (blue)
+}
+
+interface Text<T : Any> : Widget<T> {
+  fun text(text: String)
+  fun bgColor(color: Int)
+}

redwood-lazylayout-shared-test/src/iosMain/kotlin/app/cash/redwood/lazylayout/utils.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.redwood.lazylayout
+
+import platform.UIKit.UIColor
+
+fun Int.toUIColor(): UIColor {
+  return UIColor(
+    red = ((this shr 16) and 0xff) / 255.0,
+    green = ((this shr 8) and 0xff) / 255.0,
+    blue = (this and 0xff) / 255.0,
+    alpha = ((this shr 24) and 0xff) / 255.0,
+  )
+}