Export backupV2 using actual desired file format.

app/src/test/java/org/thoughtcrime/securesms/backup/v2/stream/EncryptedBackupReaderWriterTest.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.backup.v2.stream
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.thoughtcrime.securesms.backup.v2.proto.AccountData
+import org.thoughtcrime.securesms.backup.v2.proto.Frame
+import org.thoughtcrime.securesms.util.Util
+import org.whispersystems.signalservice.api.backup.BackupKey
+import org.whispersystems.signalservice.api.push.ServiceId.ACI
+import java.io.ByteArrayOutputStream
+import java.util.UUID
+
+class EncryptedBackupReaderWriterTest {
+
+  @Test
+  fun `can read back all of the frames we write`() {
+    val key = BackupKey(Util.getSecretBytes(32))
+    val aci = ACI.from(UUID.randomUUID())
+
+    val outputStream = ByteArrayOutputStream()
+
+    val frameCount = 10_000
+    EncryptedBackupWriter(key, aci, outputStream, append = { outputStream.write(it) }).use { writer ->
+      for (i in 0 until frameCount) {
+        writer.write(Frame(account = AccountData(username = "username-$i")))
+      }
+    }
+
+    val ciphertext: ByteArray = outputStream.toByteArray()
+
+    val frames: List<Frame> = EncryptedBackupReader(key, aci, ciphertext.size.toLong()) { ciphertext.inputStream() }.use { reader ->
+      reader.asSequence().toList()
+    }
+
+    assertEquals(frameCount, frames.size)
+
+    for (i in 0 until frameCount) {
+      assertEquals("username-$i", frames[i].account?.username)
+    }
+  }
+}