MockVpn is very difficult to use because it requires the test
caller keeping track of both the MockVpn object and an
accompanying TestNetworkAgentWrapper.
It's also not very realistic: for example, connect() doesn't
actually connect anything, it just makes it so that if
ConnectivityService tries to update the capabilities, the attempt
will not be ignored. Also, unlike the real code in Vpn, it
connects with empty NetworkCapabilities (in particular, with
empty UID ranges).
Make this easier to use and a bit more realistic by:
- Allowing TestNetworkAgentWrapper to take a "NetworkCapabilities
template" that will form the initial capabilities sent when the
agent registers with ConnectivityService. This allows the VPN
to register its agent with its UID ranges already set, like the
production code does.
- Providing separate methods to register the NetworkAgent and
mark it connected for cases where the test needs to make
changes to the NetworkAgent before connecting (e.g., poking
NetworkMonitor).
- Putting the TestNetworkAgentWrapper inside MockVpn and driving
it through MockVpn's methods. In order not to have too many
wrapper functions (and because we can't delegate like in
Kotlin), there's still an agent() method that returns the
TestNetworkAgentWrapper.
Bug: 172870110
Test: test-only change
Change-Id: I749ff325bc13ac96f512270b86d1f67686eec378
Merged-In: I749ff325bc13ac96f512270b86d1f67686eec378
02e6be7824