diff --git a/tests/cts/net/src/android/net/cts/ApfIntegrationTest.kt b/tests/cts/net/src/android/net/cts/ApfIntegrationTest.kt
index 7a4d90b..0e57019 100644
--- a/tests/cts/net/src/android/net/cts/ApfIntegrationTest.kt
+++ b/tests/cts/net/src/android/net/cts/ApfIntegrationTest.kt
@@ -39,6 +39,7 @@
 import android.system.OsConstants.IPPROTO_ICMP
 import android.system.OsConstants.SOCK_DGRAM
 import android.system.OsConstants.SOCK_NONBLOCK
+import android.util.Log
 import androidx.test.platform.app.InstrumentationRegistry
 import com.android.compatibility.common.util.PropertyUtil.getVsrApiLevel
 import com.android.compatibility.common.util.SystemUtil.runShellCommand
@@ -62,8 +63,8 @@
 import java.lang.Thread
 import java.net.InetSocketAddress
 import java.util.concurrent.CompletableFuture
-import java.util.concurrent.ExecutionException
 import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
 import kotlin.random.Random
 import kotlin.test.assertFailsWith
 import kotlin.test.assertNotNull
@@ -83,6 +84,8 @@
 @AppModeFull(reason = "CHANGE_NETWORK_STATE permission can't be granted to instant apps")
 @RunWith(DevSdkIgnoreRunner::class)
 @NetworkStackModuleTest
+// ByteArray.toHexString is experimental API
+@kotlin.ExperimentalStdlibApi
 class ApfIntegrationTest {
     companion object {
         private val PING_DESTINATION = InetSocketAddress("8.8.8.8", 0)
@@ -111,7 +114,7 @@
             private val network: Network
     ) : PacketReader(handler, RCV_BUFFER_SIZE) {
         private var sockFd: FileDescriptor? = null
-        private val futureReply = CompletableFuture<ByteArray>()
+        private var futureReply: CompletableFuture<ByteArray>? = null
 
         override fun createFd(): FileDescriptor {
             // sockFd is closed by calling super.stop()
@@ -124,7 +127,9 @@
 
         override fun handlePacket(recvbuf: ByteArray, length: Int) {
             // Only copy the ping data and complete the future.
-            futureReply.complete(recvbuf.sliceArray(8..<length))
+            val result = recvbuf.sliceArray(8..<length)
+            Log.i(TAG, "Received ping reply: ${result.toHexString()}")
+            futureReply!!.complete(recvbuf.sliceArray(8..<length))
         }
 
         fun sendPing(data: ByteArray) {
@@ -142,20 +147,18 @@
             // +-+-+-+-+-
             val icmpHeader = byteArrayOf(0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00)
             val packet = icmpHeader + data
+            Log.i(TAG, "Sent ping: ${packet.toHexString()}")
+            futureReply = CompletableFuture<ByteArray>()
             Os.sendto(sockFd!!, packet, 0, packet.size, 0, PING_DESTINATION)
         }
 
         fun expectPingReply(): ByteArray {
-            return futureReply.get(TIMEOUT_MS, TimeUnit.MILLISECONDS)
+            return futureReply!!.get(TIMEOUT_MS, TimeUnit.MILLISECONDS)
         }
 
         fun expectPingDropped() {
-            assertFailsWith(IllegalStateException::class) {
-                try {
-                    futureReply.get(TIMEOUT_MS, TimeUnit.MILLISECONDS)
-                } catch (e: ExecutionException) {
-                    throw e.cause!!
-                }
+            assertFailsWith(TimeoutException::class) {
+                futureReply!!.get(TIMEOUT_MS, TimeUnit.MILLISECONDS)
             }
         }
 
@@ -303,7 +306,7 @@
     }
 
     fun installProgram(bytes: ByteArray) {
-        val prog = HexDump.toHexString(bytes, 0 /* offset */, bytes.size, false /* upperCase */)
+        val prog = bytes.toHexString()
         val result = runShellCommandOrThrow("cmd network_stack apf $ifname install $prog").trim()
         // runShellCommandOrThrow only throws on S+.
         assertThat(result).isEqualTo("success")