Notes

Jetpack Compose: Testing & Semantics

2 min read

What Are Semantics?

A metadata layer that describes what a UI element means or does, not just how it looks.

  • Drives both accessibility (TalkBack, screen readers) and testing tooling
  • Makes UI elements more meaningful and testable

Semantics Tree

  • Parallel to the composition tree
  • Each “node” holds properties like text, role, state, and custom actions
  • Built-in components (Text, Icon, Switch) automatically populate common properties

How Tests Use Semantics

Locate nodes by property

val switchMatcher = SemanticsMatcher.expectValue(
    SemanticsProperties.Role, Role.Switch
)
composeTestRule.onNode(switchMatcher)
   .performClick()
   .assertIsOff()
  • Assert state (checked/unchecked, enabled/disabled, content matches)
  • Perform interactions (click, swipe, custom semantic actions)

Why It Matters

Testability:

  • Find elements by purpose (role, description) rather than view IDs or hierarchy
  • Results in stable, maintainable tests that don’t break if you refactor layout

Accessibility:

  • Ensures assistive services can navigate and announce the UI meaningfully
  • Aligns test coverage with real-world user interactions

Custom Semantics

For custom or low-level components, add semantics manually:

@Composable
fun Subsection(text: String) {
  Text(
    text = text,
    style = MaterialTheme.typography.headlineSmall,
    modifier = Modifier.semantics { heading() }
  )
}

Use Modifier.semantics { … }, clearAndSetSemantics { … }, or merging strategies to tailor the semantics tree.

Inspection & Debugging

Print the semantics tree to log or view in Layout Inspector:

composeTestRule.onRoot(useUnmergedTree = true)
    .printToLog("SEMANTICS")

Switch between merged/unmerged views to verify how props combine.

References

To learn more about Jetpack Compose and Android development:

Graph View

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