Add demonstration unittest for TetherInterfaceSM

Prove that the concept works by writing a trivial test.

Bug: 28833951
Test: `runtest frameworks-services -c
  com.android.server.connectivity.tethering.TetherInterfaceSMTest`

Change-Id: I51911cef7f0d5165221845070befd085497c21a6

services/tests/servicestests/Android.mk

@@ -12,6 +12,7 @@ LOCAL_MODULE_TAGS := tests
 LOCAL_SRC_FILES := $(call all-java-files-under, src)
 
 LOCAL_STATIC_JAVA_LIBRARIES := \
+    frameworks-base-testutils \
     services.core \
     services.devicepolicy \
     services.net \

services/tests/servicestests/src/com/android/server/connectivity/tethering/TetherInterfaceSMTest.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.connectivity.tethering;
+
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+import android.net.INetworkStatsService;
+import android.os.INetworkManagementService;
+import android.os.test.TestLooper;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+
+public class TetherInterfaceSMTest {
+    private static final String IFACE_NAME = "testnet1";
+
+    @Mock private INetworkManagementService mNMService;
+    @Mock private INetworkStatsService mStatsService;
+    @Mock private IControlsTethering mTetherHelper;
+
+    private final TestLooper mLooper = new TestLooper();
+    private final Object mMutex = new Object();
+    private TetherInterfaceSM mTestedSm;
+
+    @Before
+    public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+        mTestedSm = new TetherInterfaceSM(IFACE_NAME, mLooper.getLooper(), false, mMutex,
+                mNMService, mStatsService, mTetherHelper);
+        mTestedSm.start();
+    }
+
+    @Test
+    public void shouldDoNothingUntilRequested() {
+        final int [] NOOP_COMMANDS = {
+            TetherInterfaceSM.CMD_TETHER_MODE_DEAD,
+            TetherInterfaceSM.CMD_TETHER_UNREQUESTED,
+            TetherInterfaceSM.CMD_INTERFACE_UP,
+            TetherInterfaceSM.CMD_CELL_DUN_ERROR,
+            TetherInterfaceSM.CMD_IP_FORWARDING_ENABLE_ERROR,
+            TetherInterfaceSM.CMD_IP_FORWARDING_DISABLE_ERROR,
+            TetherInterfaceSM.CMD_START_TETHERING_ERROR,
+            TetherInterfaceSM.CMD_STOP_TETHERING_ERROR,
+            TetherInterfaceSM.CMD_SET_DNS_FORWARDERS_ERROR,
+            TetherInterfaceSM.CMD_TETHER_CONNECTION_CHANGED
+        };
+        for (int command : NOOP_COMMANDS) {
+            mTestedSm.sendMessage(command);
+            dispatchUntilIdle();
+            // None of those commands should trigger us to request action from
+            // the rest of the system.
+            verifyNoMoreInteractions(mNMService);
+            verifyNoMoreInteractions(mStatsService);
+            verifyNoMoreInteractions(mTetherHelper);
+        }
+    }
+
+    private void dispatchUntilIdle() {
+        for (int i = 0; i < 100; i++) {
+            if (mLooper.isIdle()) {
+                return;
+            }
+            mLooper.dispatchAll();
+        }
+        throw new RuntimeException("Failed to clear message loop.");
+    }
+}