test: add test to ensure that feature flags are sent during a ping an…

…d warm rpc (#2425)


Change-Id: I7d8ac74eae66d34de453b0cd799f45474d6ff0f7

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
- [ ] Make sure to open an issue as a [bug/issue](https://togithub.com/googleapis/java-bigtable/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)
- [ ] Rollback plan is reviewed and LGTMed
- [ ] All new data plane features have a completed end to end testing plan

Fixes #<issue_number_goes_here> ☕️

If you write sample code, please follow the [samples format](
https://togithub.com/GoogleCloudPlatform/java-docs-samples/blob/main/SAMPLE_FORMAT.md).

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubTest.java

@@ -87,6 +87,7 @@
 import com.google.cloud.bigtable.data.v2.stub.metrics.NoopMetricsProvider;
 import com.google.cloud.bigtable.data.v2.stub.sql.ExecuteQueryCallable;
 import com.google.cloud.bigtable.data.v2.stub.sql.SqlServerStream;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Queues;
 import com.google.common.io.BaseEncoding;
@@ -285,6 +286,28 @@ public void testFeatureFlags() throws InterruptedException, IOException, Executi
     assertThat(featureFlags.getLastScannedRowResponses()).isTrue();
   }
 
+  @Test
+  public void testPingAndWarmFeatureFlags()
+      throws InterruptedException, IOException, ExecutionException {
+    EnhancedBigtableStubSettings settings =
+        defaultSettings.toBuilder().setRefreshingChannel(true).build();
+    try (EnhancedBigtableStub ignored = EnhancedBigtableStub.create(settings)) {
+      Preconditions.checkState(
+          !fakeDataService.pingRequests.isEmpty(), "Ping request was not sent during setup");
+      Metadata metadata = metadataInterceptor.headers.take();
+
+      String encodedFeatureFlags =
+          metadata.get(Key.of("bigtable-features", Metadata.ASCII_STRING_MARSHALLER));
+      FeatureFlags featureFlags =
+          FeatureFlags.parseFrom(BaseEncoding.base64Url().decode(encodedFeatureFlags));
+
+      assertThat(featureFlags.getReverseScans()).isTrue();
+      assertThat(featureFlags.getLastScannedRowResponses()).isTrue();
+      assertThat(featureFlags.getRoutingCookie()).isTrue();
+      assertThat(featureFlags.getRetryInfo()).isTrue();
+    }
+  }
+
   @Test
   public void testCheckAndMutateRequestResponseConversion()
       throws ExecutionException, InterruptedException {