fix: Set up DirectPath e2e tests correctly (#780)

* chore: add DirectPath fallback integration test * fix: Set up DirectPath e2e tests correctly

Author: mohanli-ml

google-cloud-spanner/src/test/java/com/google/cloud/spanner/GceTestEnvConfig.java

@@ -70,12 +70,6 @@ public GceTestEnvConfig() {
  SpannerOptions.newBuilder()
  .setAutoThrottleAdministrativeRequests()
  .setTrackTransactionStarter();
- InstantiatingGrpcChannelProvider.Builder defaultChannelProviderBuilder =
- InstantiatingGrpcChannelProvider.newBuilder();
- if (attemptDirectPath) {
- builder.setChannelProvider(
- defaultChannelProviderBuilder.setEndpoint(DIRECT_PATH_ENDPOINT).build());
- }
  if (!projectId.isEmpty()) {
  builder.setProjectId(projectId);
  }
@@ -96,6 +90,16 @@ public GceTestEnvConfig() {
  interceptorProvider.with(new DirectPathAddressCheckInterceptor(directPathTestScenario));
  }
  builder.setInterceptorProvider(interceptorProvider);
+ // DirectPath tests need to set a custom endpoint to the ChannelProvider
+ InstantiatingGrpcChannelProvider.Builder customChannelProviderBuilder =
+ InstantiatingGrpcChannelProvider.newBuilder();
+ if (attemptDirectPath) {
+ customChannelProviderBuilder
+ .setEndpoint(DIRECT_PATH_ENDPOINT)
+ .setAttemptDirectPath(true)
+ .setInterceptorProvider(interceptorProvider);
+ builder.setChannelProvider(customChannelProviderBuilder.build());
+ }
  options = builder.build();
  }