Test a Composable

In order to test a @Composable function, you must first declare an instance variable of the ComposableScreenshotRule class. You will be using this rule instead of the default ScreenshotTestRule.

ComposableScreenshotRule provides a setCompose() method which accepts a composable function in which you can specify your own custom compositions. You can invoke the setCompose() method on the rule instance and declare any Compose UI functions you wish to test.

The contents of setCompose() are rendered as the contents of the provided ComposableTestActivity. ComposableTestActivity is a simple activity with single root ComposeView with a Color.White background.

The ComposeView provided by ComposableTestActivity is defined with WRAP_CONTENT layout parameters and so the captured image will be constrained to fit only the bounds of the @Composable.

If necessary, you can access the root view with the identifier dev.testify.compose.R.id.compose_container.

ComposableScreenshotScenarioRule

As ActivityTestRule is deprecated, the Android SDK now recommends the usage of ActivityScenario as the modern alternative. Testify provides ComposableScreenshotScenarioRule which works in conjunction with ActivityScenario to easily add screenshot tests to scenario-based UI tests.

ComposableScreenshotScenarioRule is more flexible than the older ComposableScreenshotRule as it no longer requires you to couple the rule's instantiatiation with a specific Activity subclass. This allows the flexibility of testing multiple different activities in the same test class.

Screenshot test integration with ActivityScenario is achieved via the withScenario() function. An active instance of a scenario must be provided to Testify prior to calling assertSame(). Typically, this is done by passing the scaneario instance returned by ActivityScenario.launch to the ScreenshotScenarioRule instance within a use {} block.

tip

To enable Android Studio Plugin integration with your tests, each test method should be annotated with the @ScreenshotInstrumentation annotation.

import androidx.test.core.app.launchActivity
import dev.testify.ComposableTestActivity
import dev.testify.annotation.ScreenshotInstrumentation
import dev.testify.compose.scenario.ComposableScreenshotScenarioRule
import org.junit.Rule
import org.junit.Test

class ComposableScreenshotTest {

    @get:Rule val rule = ComposableScreenshotScenarioRule()

    @ScreenshotInstrumentation
    @Test
    fun default() {
        launchActivity<ComposableTestActivity>().use { scenario ->
            rule
                .withScenario(scenario)
                .setCompose {
                    Text(text = "Hello, Testify!")
                }
                .assertSame()
        }
    }
}

tip

The helper extension method launchComposableTestActivity is provided to simplify the launching of the provided ComposableTestActivity test harness activity.

ComposableScreenshotRule

caution

ActivityTestRule is deprecated

Use androidx.test.core.app.ActivityScenario instead with ComposableScreenshotScenarioRule.

Example

class ComposableScreenshotTest {

    @get:Rule val rule = ComposableScreenshotRule()

    @ScreenshotInstrumentation
    @Test
    fun default() {
        rule
            .setCompose {
                Text(text = "Hello, Testify!")
            }
            .assertSame()
    }
}