### Question:
TransportManager { @Deprecated @Nullable String selectTransport(String transportName) { synchronized (mTransportLock) { String prevTransport = mCurrentTransportName; mCurrentTransportName = transportName; return prevTransport; } } TransportManager(Context context, Set<ComponentName> whitelist, String selectedTransport); @VisibleForTesting  TransportManager(
            Context context,
            Set<ComponentName> whitelist,
            String selectedTransport,
            TransportClientManager transportClientManager); void setOnTransportRegisteredListener(OnTransportRegisteredListener listener); String getTransportName(ComponentName transportComponent); String getTransportDirName(ComponentName transportComponent); String getTransportDirName(String transportName); @Nullable Intent getTransportConfigurationIntent(String transportName); String getTransportCurrentDestinationString(String transportName); @Nullable Intent getTransportDataManagementIntent(String transportName); @Nullable String getTransportDataManagementLabel(String transportName); boolean isTransportRegistered(String transportName); void forEachRegisteredTransport(Consumer<String> transportConsumer); void updateTransportAttributes(
            ComponentName transportComponent,
            String name,
            @Nullable Intent configurationIntent,
            String currentDestinationString,
            @Nullable Intent dataManagementIntent,
            @Nullable String dataManagementLabel); @Nullable TransportClient getTransportClient(String transportName, String caller); TransportClient getTransportClientOrThrow(String transportName, String caller); @Nullable TransportClient getCurrentTransportClient(String caller); TransportClient getCurrentTransportClientOrThrow(String caller); void disposeOfTransportClient(TransportClient transportClient, String caller); @WorkerThread int registerAndSelectTransport(ComponentName transportComponent); @WorkerThread void registerTransports(); void dumpTransportClients(PrintWriter pw); void dumpTransportStats(PrintWriter pw); @VisibleForTesting
    static final String SERVICE_ACTION_TRANSPORT_HOST; }### Answer:
@Test public void testSelectTransport() throws Exception { setUpPackage(PACKAGE_A, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED); setUpTransports(mTransportA1, mTransportA2); TransportManager transportManager = createTransportManager(null, mTransportA1, mTransportA2); String transport1 = transportManager.selectTransport(mTransportA1.transportName); String transport2 = transportManager.selectTransport(mTransportA2.transportName); assertThat(transport1).isNull(); assertThat(transport2).isEqualTo(mTransportA1.transportName); }