Use ConnectivityManager.MockHelpers

Telephony tests mock ConnectivityManager private methods
but don't have access to their private types. In the
context that Connectivity would like to change the return
type of CM#registerNetworkAgent to a private type, offer
a simple solution to still mock it without having to
remove all checks from Telephony.

See also aosp/3543704

Test: FrameworksTelephonyTests
Change-Id: I61e5fa4b8ba6d8825d2c41bae907a0492c1f8b14
Merged-In: I61e5fa4b8ba6d8825d2c41bae907a0492c1f8b14

tests/telephonytests/src/com/android/internal/telephony/ContextFixture.java

diff --git a/tests/telephonytests/src/com/android/internal/telephony/ContextFixture.java b/tests/telephonytests/src/com/android/internal/telephony/ContextFixture.java
index 9788320..abff2af 100644
--- a/tests/telephonytests/src/com/android/internal/telephony/ContextFixture.java
+++ b/tests/telephonytests/src/com/android/internal/telephony/ContextFixture.java
@@ -809,8 +809,9 @@
         doReturn(mBundle).when(mCarrierConfigManager).getConfig();
         doReturn(mBundle).when(mCarrierConfigManager).getConfigForSubId(anyInt(), anyString());
         doAnswer(invocation -> mNetworkId++).when(mNetwork).getNetId();
-        doReturn(mNetwork).when(mConnectivityManager).registerNetworkAgent(
-                any(), any(), any(), any(), any(), any(), anyInt());
+        doReturn(ConnectivityManager.MockHelpers.registerNetworkAgentResult(mNetwork, null))
+                .when(mConnectivityManager).registerNetworkAgent(
+                        any(), any(), any(), any(), any(), any(), anyInt());
 
         doReturn(true).when(mEuiccManager).isEnabled();