Compose Preview Screenshot Testing

Screenshot testing is an effective way to verify how your UI looks to users. The Compose Preview Screenshot Testing tool combines the simplicity and features of composable previews with the productivity gains of running host-side screenshot tests. Compose Preview Screenshot Testing is designed to be as straightforward to use as composable previews.

A screenshot test is an automated test that takes a screenshot of a piece of UI and then compares it against a previously approved reference image. If the images don't match, the test fails and produces an HTML report to help you compare and find the differences.

With the Compose Preview Screenshot Testing tool, you can:

• Use @PreviewTest to create screenshot tests for existing or new composable previews.
• Generate reference images from those composable previews.
• Generate an HTML report that identifies changes to those previews after you make code changes.
• Use @Preview parameters, such as uiMode or fontScale, and multi-previews to help you scale your tests.
• Modularize your tests with the new screenshotTest source set.

IDE integration

While you can use the Compose Preview Screenshot Testing tool by running the underlying Gradle tasks (updateScreenshotTest and validateScreenshotTest) manually, Android Studio Otter 3 Feature Drop Canary 4 introduces a full IDE integration. This lets you generate reference images, run tests, and analyze validation failures entirely within the IDE. Here are some of the key features:

• In-editor gutter icons. You can now run tests or update reference images directly from the source code. Green run icons appear in the gutter next to composables and classes annotated with @PreviewTest.
  • Run screenshot tests. Execute tests specifically for a single function or for an entire class.
  • Add or update reference images. Trigger the update flow specifically for the selected scope.

• Interactive reference management. Updating reference images is now safer and more granular.
  • New reference image generation dialog. Instead of running a bulk Gradle task, a new dialog lets you visualize and select exactly which previews to generate or update.
  • Preview variations. The dialog lists all preview variations (such as light theme or dark theme, or different devices) individually, allowing you to select or clear specific items before generating images.

• Integrated test results and diff viewer. View results without leaving the IDE.
  • Unified run panel. Screenshot test results appear in the standard Run tool window. Tests are grouped by class and function, with pass or fail status clearly marked.
  • Visual diff tool. When a test fails, the Screenshot tab lets you compare the Reference, Actual, and Diff images side-by-side.
  • Detailed attributes. An Attributes tab provides metadata on failed tests, including match percentage, image dimensions, and the specific preview configuration used (for example, uiMode or fontScale).

• Flexible test scoping. You can now execute screenshot tests with various scopes directly from the Project View. Right-click a module, directory, file, or class to run screenshot tests specifically for that selection.

Requirements

To use Compose Preview Screenshot Testing through the full IDE integration, your project must meet the following requirements:

• Android Studio Panda 1 Canary 4 or higher.
• Android Gradle Plugin (AGP) version 9.0 or higher.
• Compose Preview Screenshot Testing plugin version 0.0.1-alpha14 or higher.
• Kotlin version 2.2.10 or higher.
• JDK version 17 or higher.
• Compose enabled for your project. We recommend enabling Compose using the Compose Compiler Gradle plugin.

If you only want to use the underlying Gradle tasks without the IDE integration, the requirements are as follows:

• Android Gradle Plugin (AGP) version 8.5.0 or higher.
• Compose Preview Screenshot Testing plugin version 0.0.1-alpha14 or higher.
• Kotlin version 1.9.20 or higher. We recommend using Kotlin 2.0 or higher so you can use the Compose Compiler Gradle plugin.
• JDK version 17 or higher.
• Compose enabled for your project. We recommend enabling Compose using the Compose Compiler Gradle plugin.

Setup

Both the integrated tool and the underlying Gradle tasks rely on the Compose Preview Screenshot Testing plugin. To set up the plugin, follow these steps:

1. Enable the experimental property in your project's gradle.properties file.

   android.experimental.enableScreenshotTest=true
   

2. In the android {} block of your module-level build.gradle.kts file, enable the experimental flag to use the screenshotTest source set.

   android {
       experimentalProperties["android.experimental.enableScreenshotTest"] = true
   }
   

3. Add the com.android.compose.screenshot plugin, version 0.0.1-alpha14 to your project.

   1. Add the plugin to your version catalogs file:

      [versions]
      agp = "9.0.0-rc03"
      kotlin = "2.1.20"
      screenshot = "0.0.1-alpha14"
      
      [plugins]
      screenshot = { id = "com.android.compose.screenshot", version.ref = "screenshot"}
      

   2. In your module-level build.gradle.kts file, add the plugin in the plugins {} block:

      plugins {
          alias(libs.plugins.screenshot)
      }
      

4. Add the screenshot-validation-api and ui-tooling dependencies.

   1. Add them to your version catalogs:

      [libraries]
      screenshot-validation-api = { group = "com.android.tools.screenshot", name = "screenshot-validation-api", version.ref = "screenshot"}
      androidx-ui-tooling = { group = "androidx.compose.ui", name = "ui-tooling"}
      

   2. Add them to your module-level build.gradle.kts file:

      dependencies {
        screenshotTestImplementation(libs.screenshot.validation.api)
        screenshotTestImplementation(libs.androidx.ui.tooling)
      }
      

Designate composable previews to use for screenshot tests

To designate the composable previews you want to use for screenshot tests, mark the previews with the @PreviewTest annotation. The previews must be located in the new screenshotTest source set, for example:

app/src/screenshotTest/kotlin/com/example/yourapp/ ExamplePreviewScreenshotTest.kt

You can add more composables or previews, including multi-previews, in this file or other files created in the same source set.

package com.example.yourapp

import androidx.compose.runtime.Composable
import androidx.compose.ui.tooling.preview.Preview
import com.android.tools.screenshot.PreviewTest
import com.example.yourapp.ui.theme.MyApplicationTheme

@PreviewTest
@Preview(showBackground = true)
@Composable
fun GreetingPreview() {
    MyApplicationTheme {
        Greeting("Android!")
    }
}

Generate reference images

After you set up a test class, you need to generate reference images for each preview. These reference images are used to identify changes later, after you make code changes. To generate reference images for your composable preview screenshot tests, follow the instructions in this section for the IDE integration or for the Gradle tasks.

In the IDE

Click the gutter icon next to a @PreviewTest function and select Add/Update Reference Images. Select the previews in the dialog and click Add.

With the Gradle tasks

Run the following Gradle task:

• Linux and macOS: ./gradlew updateDebugScreenshotTest (./gradlew :{module}:update{Variant}ScreenshotTest)
• Windows: gradlew updateDebugScreenshotTest (gradlew :{module}:update{Variant}ScreenshotTest)

After the task completes, find the reference images in app/src/screenshotTestDebug/reference ({module}/src/screenshotTest{Variant}/reference).

Generate a test report

Once the reference images exist, generate a test report by following the instructions in this section for the IDE integration or for the Gradle tasks.

In the IDE

Click the gutter icon next to a @PreviewTest function and select Run 'ScreenshotTests'.

If a test fails, click the test name in the Run panel. Select the Screenshot tab to inspect the image diff using the integrated zoom and pan controls.

With the Gradle tasks

Run the validate task to take a new screenshot and compare it with the reference image:

• Linux and macOS: ./gradlew validateDebugScreenshotTest (./gradlew :{module}:validate{Variant}ScreenshotTest)
• Windows: gradlew validateDebugScreenshotTest (gradlew :{module}:validate{Variant}ScreenshotTest)

The verification task creates an HTML report at {module}/build/reports/screenshotTest/preview/{variant}/index.html.

Known issues

• Kotlin Multiplatform (KMP): Both the IDE and the underlying plugin are engineered exclusively for Android projects. They don't support non-Android targets in KMP projects.

You can find the complete list of current known issues in the tool's issue tracker component. Report any other feedback and issues through the issue tracker.

Release updates

For a full list of release updates, see the release notes.