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AsyncTask Idling Resource

Purpose

Synchronizes Espresso UI tests with background { } async operations to prevent flaky tests caused by race conditions.

How It Works

  1. AsyncTaskCallback interface in AsyncUtils.kt defines onTaskStarted() / onTaskCompleted()
  2. AsyncOperation calls these hooks during task lifecycle
  3. globalAsyncTaskCallback is a @Volatile global that tests can set
  4. AsyncTaskIdlingResource implements both IdlingResource and AsyncTaskCallback
  5. Espresso waits until counter reaches 0 before proceeding

Usage

Tests using UITestFixture get this automatically:

@Before
fun setup() {
    fixture.setup(waitForAsyncTasks = true)  // Registers idling resource
}

@After
fun teardown() {
    fixture.cleanup()  // Unregisters and nulls globalAsyncTaskCallback
}

Production Impact

None. The callback defaults to null, so production code just does a few no-op null checks.

Added: December 2024