Screenshot-based visual regression testing for Jetpack Compose captures a screen, compares it with an approved reference image (often called a golden), and reports differences for review. The mismatch is a prompt to investigate—not proof that the UI is wrong. Android Developers calls screenshot testing the recommended way to verify visual attributes in Compose UIs: official screenshot-testing documentation.
What a Compose screenshot test checks
A screenshot test checks rendered appearance in the test environment. The test produces a new image and compares it with a reference your team has approved. If pixels or other image-comparison criteria differ, the test reports a change so a developer can decide whether it is an unintended regression or an intentional design update.
This makes screenshot tests useful for catching visual changes that are easy to miss in code review: spacing, colors, typography, component sizing, and layout. They do not, by themselves, establish that interactions work correctly or that the screen renders identically on every physical device. Use interaction or device tests when runtime behavior, system integration, or device-specific rendering is the question.
Set up the official Compose Preview Screenshot Testing workflow
Android’s official Compose Preview Screenshot Testing tool turns composable previews into host-side screenshot tests. Its documentation currently labels the tool experimental and warns that APIs may change substantially during the alpha phase. Check the current setup instructions and project compatibility before adopting it.
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- Enable screenshot testing. Add the experimental screenshot-test property to the project’s
gradle.properties, following the current official instructions. - Configure the Android module. Enable the screenshot-test source set in the module configuration and add the
com.android.compose.screenshotplugin. The documentation version identified for this article is0.0.1-alpha16; verify the live version rather than copying that snapshot blindly. - Add preview tests. Put screenshot test functions in the
screenshotTestsource set and annotate the preview functions with@PreviewTest. - Create approved references. In the IDE, use Add/Update Reference Images, or run the documented
updateDebugScreenshotTestGradle task. For a particular module or variant, use its corresponding task. - Validate changes. Run
validateDebugScreenshotTest, or the corresponding module/variant task, to render the previews and compare them with the saved references.
Because plugin versions and integration details can change, use the live documentation for exact Gradle syntax and compatibility. The available evidence does not establish a complete compatibility matrix for Android Gradle Plugin, Kotlin, Compose, and Android Studio versions.
Choose previews that cover real visual risks
A test only covers the configurations represented by its previews. Use preview parameters such as uiMode and fontScale, and multi-previews where appropriate, to check meaningful differences such as light and dark appearance or enlarged text. Select the matrix according to the screen’s design risks rather than trying to generate every possible combination.
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For example, a screen whose layout is sensitive to text wrapping may merit a larger font-scale preview; a surface with different color treatment by theme may merit both light and dark previews. These are coverage choices, not guarantees that every operating-system or device variation has been tested.
Review failures before updating references
When validation fails, inspect the reference, newly rendered image, and diff together. The official workflow provides an HTML report and an IDE diff view; reports can include the match percentage, image dimensions, and preview configuration. Use these details to locate and understand the change in context.
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- Identify which preview configuration failed and confirm the rendered image is the expected screen state.
- Inspect the reference, actual image, and diff to see what changed and where.
- Decide whether the difference is unintended, or reflects an intentional design or code update.
- Fix an unintended change. If the visual change is intended and accepted, regenerate the reference image and review that update as part of the change.
Do not update goldens simply to make a failing test pass: that would approve the new appearance without deciding whether it is correct.
Where references and reports live
The official tool stores reference images under a path of the form {module}/src/screenshotTest{Variant}/reference. File names combine the fully qualified test-function name with a hash of the preview parameters. Renaming a function annotated with @PreviewTest breaks its association with existing references, so regenerate the reference images after such a rename.
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The Gradle validation flow creates an HTML report under the module’s build reports directory. The IDE integration can present the test result alongside the reference, actual, and diff images, which helps connect a failing comparison to the preview that produced it.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Official preview tool or Roborazzi?
Both approaches document preview-based screenshot workflows, but their fit depends on project needs. The official tool is engineered exclusively for Android and does not support non-Android Kotlin Multiplatform targets. Roborazzi documents generating screenshot tests from Compose previews as well as manually capturing previews; its documented preview scanner does not support every option on Compose’s @Preview annotation.
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| Consideration | Official Compose Preview Screenshot Testing | Roborazzi |
|---|---|---|
| Preview workflow | Official tool uses composable previews as host-side screenshot tests and documents @PreviewTest. |
Project documentation describes generating screenshot tests from Compose previews and manually capturing previews. |
| Preview-option coverage | Supports configurations such as uiMode and fontScale; check current documentation for options needed by your project. |
Documented preview scanner integration does not support all Compose @Preview options. |
| Platform scope | Android-only; the documentation says non-Android Kotlin Multiplatform targets are not supported. | Not stated in the cited project documentation for this comparison. |
| Tool maturity | Documentation labels it experimental and says APIs may change during alpha. | Not stated in the cited project documentation for this comparison. |
| Performance or accuracy benchmark | No controlled comparison established. | No controlled comparison established. |
Choose based on preview integration, required preview configurations, project and build-tool compatibility, how references and failure reports fit your workflow, and whether you need host-side or instrumented rendering. Android Developers notes that third-party tools can offer instrumented and local screenshot tests; the available sources do not establish that either option is categorically faster or more accurate.
Plan for host-side resource use
The official workflow runs host-side tests and can be memory-intensive. Its documentation gives android.compose.screenshot.maxHeapSize=4g as an example of increasing the test JVM heap setting. Treat this as a configuration option, not a measured performance recommendation: adjust resources based on your environment and test workload.
Screenshot tests answer a visual-comparison question for the rendering setup used by the chosen tool. Keep device or interaction tests for questions that depend on runtime behavior, system integration, or a particular device’s rendering.
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