Fix test failures related to subchannel list ordering by using result…

… value rather than getLast()

rls/src/test/java/io/grpc/rls/RlsLoadBalancerTest.java

@@ -242,7 +242,7 @@ public void lb_working_withDefaultTarget_noRlsResponse() throws Exception {
     // Search that when the RLS server doesn't respond, that fallback is used
     res = picker.pickSubchannel(
         new PickSubchannelArgsImpl(fakeSearchMethod, headers, CallOptions.DEFAULT));
-    FakeSubchannel fallbackSubchannel = subchannels.getLast();
+    FakeSubchannel fallbackSubchannel = (FakeSubchannel) res.getSubchannel();
 
     assertThat(res.getStatus().getCode()).isEqualTo(Status.Code.OK);
     assertThat(subchannelIsReady(res.getSubchannel())).isFalse();
@@ -265,21 +265,19 @@ public void lb_working_withDefaultTarget_noRlsResponse() throws Exception {
     // Make sure that when RLS starts communicating that default stops being used
     fakeThrottler.nextResult = false;
     fakeClock.forwardTime(2, TimeUnit.SECONDS); // Expires backoff cache entries
-
     // Create search subchannel
     res = picker.pickSubchannel(
         new PickSubchannelArgsImpl(fakeSearchMethod, headers, CallOptions.DEFAULT));
     assertThat(res.getSubchannel()).isNotSameInstanceAs(fallbackSubchannel);
-    FakeSubchannel searchSubchannel = subchannels.getLast();
+    FakeSubchannel searchSubchannel = (FakeSubchannel) res.getSubchannel();
     searchSubchannel.updateState(ConnectivityStateInfo.forNonError(ConnectivityState.READY));
-    assertThat(subchannelIsReady(res.getSubchannel())).isTrue();
 
     // create rescue subchannel
     res = picker.pickSubchannel(
         new PickSubchannelArgsImpl(fakeRescueMethod, headers, CallOptions.DEFAULT));
     assertThat(res.getSubchannel()).isNotSameInstanceAs(fallbackSubchannel);
     assertThat(res.getSubchannel()).isNotSameInstanceAs(searchSubchannel);
-    FakeSubchannel rescueSubchannel = subchannels.getLast();
+    FakeSubchannel rescueSubchannel = (FakeSubchannel) res.getSubchannel();
     rescueSubchannel.updateState(ConnectivityStateInfo.forNonError(ConnectivityState.READY));
 
     // all channels are failed
@@ -588,7 +586,7 @@ private static final class FakeSubchannel extends Subchannel {
     private final Attributes attributes;
     private List<EquivalentAddressGroup> eags;
     private SubchannelStateListener listener;
-    private boolean isReady;
+    private volatile boolean isReady;
 
     public FakeSubchannel(List<EquivalentAddressGroup> eags, Attributes attributes) {
       this.eags = Collections.unmodifiableList(eags);