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package com.example
import kotlin.annotation.AnnotationRetention.RUNTIME
import kotlin.annotation.AnnotationTarget.FUNCTION
* @see TracingRunListener
annotation class TraceTest
package com.example
import android.os.Debug
import android.os.SystemClock
import org.junit.runner.Description
import org.junit.runner.notification.RunListener
import timber.log.Timber
* Turns on sampling profiling on Firebase UI test methods annotated with [TraceTest]
* [TracingRunListener] is enabled for all Firebase UI tests and selectively turns on profiling by
* looking up the annotations on the test methods.
* The resulting traces are stored on the device in /sdcard/traces and can be downloaded by Firebase to
* gcloud storage with `--directories-to-pull "/sdcard/traces/"`
* Once you've downloaded the trace file, open the Profiler in Android Studio
* (Cmd + Shift + A and type Profiler). Click the + sign, select "Load from file..." and open up
* the trace file. Now go read this:
* First you'll want to select a thread in the Threads view. You're most likely interested in
* "main" and "Instr: runner name". Once you've selected a thread, Call Chart will give you a sense
* of the timeline / where CPU time is spent over time. Flame Chart is not time based but groups
* together identical stack traces, so it helps you identify calls that happens a lot.
* When looking at the Bottom Up tab, it's useful to try sorting by Total but also Self (which would
* e.g. surface thread waiting calls).
internal class TracingRunListener : RunListener() {
var tracingTest = false
private val Description.traceTest
get() = getAnnotation( != null
private val Description.traceFile
get() = "$FOLDER$className.$methodName-${SystemClock.uptimeMillis()}.trace"
override fun testRunStarted(description: Description?) {
val defaultHandler = Thread.getDefaultUncaughtExceptionHandler()
Thread.setDefaultUncaughtExceptionHandler { thread, throwable ->
stopMethodTracing("Stopped profiler trace because process crashed")
defaultHandler.uncaughtException(thread, throwable)
override fun testStarted(description: Description) {
if (description.traceTest) {
tracingTest = true
val folder = File(FOLDER)
val traceFile = description.traceFile
Timber.d("Starting a profiler trace, stored at %s", traceFile)
Debug.startMethodTracingSampling(traceFile, BUFFER_SIZE, INTERVAL_MICROS)
override fun testFinished(description: Description) {
stopMethodTracing("Stopped profiler trace because test finished")
private fun stopMethodTracing(logMessage: String) {
if (tracingTest) {
tracingTest = false
companion object {
private const val FOLDER = "/sdcard/traces/"
* A buffer of that size is immediately allocated in memory. The final files is smaller than that.
private const val BUFFER_SIZE = 50 * 1024 * 1024
private const val INTERVAL_MICROS = 1000
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