Introduce a Snapshotter interface for tests (#2322)

* Introduce a Snapshotter interface for tests

I'm attempting to test that changes to the view hierarchy don't
cause unnecessary extra layouts, so I need the parent view to
remain stable across multiple snapshots. This new Snapshotter
interface makes that straightforward.

This is currently only implemented for 'layout' tests. I'll
follow up with 'lazylayout' tests next.

* SpotlessApply

* Snapshotter for UIViewLazyListAsFlexContainerTest

* Revert incremental change

redwood-layout-composeui/src/androidUnitTest/kotlin/app/cash/redwood/layout/composeui/ComposeSnapshotter.kt

@@ -0,0 +1,29 @@
+/*
+ * 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.layout.composeui
+
+import androidx.compose.runtime.Composable
+import app.cash.paparazzi.Paparazzi
+import app.cash.redwood.layout.Snapshotter
+
+class ComposeSnapshotter(
+  private val paparazzi: Paparazzi,
+  private val widget: @Composable () -> Unit,
+) : Snapshotter {
+  override fun snapshot(name: String?) {
+    paparazzi.snapshot(composable = widget, name = name)
+  }
+}

redwood-layout-composeui/src/androidUnitTest/kotlin/app/cash/redwood/layout/composeui/ComposeUiBoxTest.kt

@@ -46,7 +46,5 @@ class ComposeUiBoxTest(
 
   override fun text(): Text<@Composable () -> Unit> = ComposeUiText()
 
-  override fun verifySnapshot(widget: @Composable () -> Unit, name: String?) {
-    paparazzi.snapshot(composable = widget, name = name)
-  }
+  override fun snapshotter(widget: @Composable () -> Unit) = ComposeSnapshotter(paparazzi, widget)
 }

redwood-layout-composeui/src/androidUnitTest/kotlin/app/cash/redwood/layout/composeui/ComposeUiFlexContainerTest.kt

@@ -60,11 +60,7 @@ class ComposeUiFlexContainerTest(
 
   override fun text() = ComposeUiText()
 
-  override fun verifySnapshot(widget: @Composable () -> Unit, name: String?) {
-    paparazzi.snapshot(name) {
-      widget()
-    }
-  }
+  override fun snapshotter(widget: @Composable () -> Unit) = ComposeSnapshotter(paparazzi, widget)
 
   class ComposeTestFlexContainer private constructor(
     private val delegate: ComposeUiFlexContainer,

redwood-layout-composeui/src/androidUnitTest/kotlin/app/cash/redwood/layout/composeui/ComposeUiSpacerTest.kt

@@ -57,7 +57,5 @@ class ComposeUiSpacerTest : AbstractSpacerTest<@Composable () -> Unit>() {
     }
   }
 
-  override fun verifySnapshot(value: @Composable () -> Unit) {
-    paparazzi.snapshot(composable = value)
-  }
+  override fun snapshotter(widget: @Composable () -> Unit) = ComposeSnapshotter(paparazzi, widget)
 }

redwood-layout-shared-test/src/commonMain/kotlin/app/cash/redwood/layout/AbstractBoxTest.kt

@@ -38,12 +38,12 @@ abstract class AbstractBoxTest<T : Any> {
     height(height)
   }
 
-  abstract fun verifySnapshot(widget: T, name: String? = null)
+  abstract fun snapshotter(widget: T): Snapshotter
 
   @Test
   fun testEmpty_Defaults() {
     val widget = box()
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   @Test
@@ -52,7 +52,7 @@ abstract class AbstractBoxTest<T : Any> {
       width(Constraint.Wrap)
       height(Constraint.Wrap)
     }
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   @Test
@@ -61,7 +61,7 @@ abstract class AbstractBoxTest<T : Any> {
       width(Constraint.Fill)
       height(Constraint.Fill)
     }
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   // testChildren
@@ -322,7 +322,7 @@ abstract class AbstractBoxTest<T : Any> {
         },
       )
     }
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   @Test
@@ -345,7 +345,7 @@ abstract class AbstractBoxTest<T : Any> {
         },
       )
     }
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   @Test
@@ -388,7 +388,7 @@ abstract class AbstractBoxTest<T : Any> {
         },
       )
     }
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   @Test
@@ -431,7 +431,7 @@ abstract class AbstractBoxTest<T : Any> {
         },
       )
     }
-    verifySnapshot(widget.value)
+    snapshotter(widget.value).snapshot()
   }
 
   @Test
@@ -444,10 +444,11 @@ abstract class AbstractBoxTest<T : Any> {
       children.insert(1, coloredText(text = mediumText(), color = Blue))
       children.insert(2, coloredText(text = shortText(), color = Green))
     }
-    verifySnapshot(widget.value, "Margin")
+    val snapshotter = snapshotter(widget.value)
+    snapshotter.snapshot("Margin")
     redColor.modifier = Modifier
     widget.children.onModifierUpdated(0, redColor)
-    verifySnapshot(widget.value, "Empty")
+    snapshotter.snapshot("Empty")
   }
 
   /** The view shouldn't crash if its displayed after being detached. */
@@ -459,16 +460,17 @@ abstract class AbstractBoxTest<T : Any> {
       horizontalAlignment(CrossAxisAlignment.Start)
       verticalAlignment(CrossAxisAlignment.Start)
     }
+    val snapshotter = snapshotter(widget.value)
 
     // Render before calling detach().
     widget.children.insert(0, coloredText(MarginImpl(10.dp), mediumText(), Green))
     widget.children.insert(1, coloredText(MarginImpl(0.dp), shortText(), Blue))
-    verifySnapshot(widget.value, "Before")
+    snapshotter.snapshot("Before")
 
     // Detach after changes are applied but before they're rendered.
     widget.children.insert(0, coloredText(MarginImpl(20.dp), longText(), Red))
     widget.children.detach()
-    verifySnapshot(widget.value, "After")
+    snapshotter.snapshot("After")
   }
 
   @Test fun testDynamicWidgetResizing() {
@@ -479,6 +481,7 @@ abstract class AbstractBoxTest<T : Any> {
         horizontalAlignment(CrossAxisAlignment.Start)
         verticalAlignment(CrossAxisAlignment.Start)
       }
+    val snapshotter = snapshotter(container.value)
 
     val a = coloredText(text = "AAA", color = Red)
       .apply { modifier = HorizontalAlignmentImpl(CrossAxisAlignment.Start) }
@@ -489,10 +492,10 @@ abstract class AbstractBoxTest<T : Any> {
     val c = coloredText(text = "CCC", color = Green)
       .apply { modifier = HorizontalAlignmentImpl(CrossAxisAlignment.End) }
       .also { container.children.insert(2, it) }
-    verifySnapshot(container.value, "v1")
+    snapshotter.snapshot("v1")
 
     b.text("BBB_v2")
-    verifySnapshot(container.value, "v2")
+    snapshotter.snapshot("v2")
   }
 
   private fun coloredText(modifier: Modifier = Modifier, text: String, color: Int) = text().apply {