Currently CS test uses a mock ProxyTracker object to verify that
the sendProxyBroadcast() is called. Also, if the network is a
default network then sendProxyBroadcast() will be indirectly
called in setDefaultProxy(). This only verifies that the method
is called but it doesn't verify that the broadcast is sent.
Instead of testing setDefaultProxy() is called, it is better to
verify that the broadcast is actually sent. Therefore, use a
real ProxyTracker in the test to verify the broadcast is sent.
Test: FrameworksNetTests:ConnectivityServiceTest
Change-Id: Id5c9e07e8326f24bd2665b4bb08f96d6d57d999c
e3879abb07