android: test Notifier drops peers removed by a full netmap

android/src/main/java/com/tailscale/ipn/ui/notifier/Notifier.kt

@@ -3,6 +3,7 @@
 
 package com.tailscale.ipn.ui.notifier
 
+import androidx.annotation.VisibleForTesting
 import com.tailscale.ipn.App
 import com.tailscale.ipn.BuildConfig
 import com.tailscale.ipn.ui.model.Empty
@@ -177,7 +178,8 @@ object Notifier {
   }
 
   @Synchronized
-  private fun updateNetworkMap(notify: Notify) {
+  @VisibleForTesting
+  internal fun updateNetworkMap(notify: Notify) {
     val initial = notify.InitialStatus
     if (initial != null) {
       userProfiles.clear()

android/src/test/kotlin/com/tailscale/ipn/ui/notifier/NotifierTest.kt

@@ -0,0 +1,78 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package com.tailscale.ipn.ui.notifier
+
+import com.tailscale.ipn.App
+import com.tailscale.ipn.UninitializedApp
+import com.tailscale.ipn.ui.model.Ipn.Notify
+import com.tailscale.ipn.ui.model.IpnState
+import com.tailscale.ipn.ui.model.NodeID
+import com.tailscale.ipn.ui.model.Tailcfg
+import com.tailscale.ipn.util.TSLog
+import com.tailscale.ipn.util.TSLog.LibtailscaleWrapper
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mockito.RETURNS_DEEP_STUBS
+import org.mockito.Mockito.mock
+
+class NotifierTest {
+  private lateinit var originalWrapper: LibtailscaleWrapper
+
+  @Before
+  fun setUp() {
+    originalWrapper = TSLog.libtailscaleWrapper
+    TSLog.libtailscaleWrapper = mock(LibtailscaleWrapper::class.java)
+    // Notifier's initializer loads the inline-share inbox from encrypted prefs.
+    UninitializedApp::class
+        .java
+        .getDeclaredField("appInstance")
+        .apply { isAccessible = true }
+        .set(null, mock(App::class.java, RETURNS_DEEP_STUBS))
+  }
+
+  @After
+  fun tearDown() {
+    TSLog.libtailscaleWrapper = originalWrapper
+  }
+
+  private fun peer(id: NodeID) =
+      IpnState.PeerStatus(ID = "s$id", NodeID = id, DNSName = "peer$id.ts.net.", UserID = 1)
+
+  private fun node(id: NodeID) =
+      Tailcfg.Node(ID = id, StableID = "s$id", Name = "peer$id.ts.net.", User = 1)
+
+  private fun seed(vararg peers: NodeID) {
+    Notifier.updateNetworkMap(
+        Notify(
+            InitialStatus =
+                IpnState.Status(
+                    Self = peer(1),
+                    Peer = peers.associate { "key$it" to peer(it) },
+                )
+        )
+    )
+  }
+
+  private fun peerIDs() = Notifier.netmap.value?.Peers?.map { it.ID }
+
+  // A full netmap from control arrives as SelfChange plus every current peer
+  // in PeersChanged; peers it dropped arrive in PeersRemoved.
+  @Test
+  fun fullNetmapDropsRemovedPeer() {
+    seed(10, 20)
+    Notifier.updateNetworkMap(
+        Notify(SelfChange = node(1), PeersChanged = listOf(node(10)), PeersRemoved = listOf(20))
+    )
+    assertEquals(listOf(10L), peerIDs())
+  }
+
+  @Test
+  fun fullNetmapDropsLastPeer() {
+    seed(10)
+    Notifier.updateNetworkMap(Notify(SelfChange = node(1), PeersRemoved = listOf(10)))
+    assertEquals(emptyList<NodeID>(), peerIDs())
+  }
+}