DefaultPrimer extends Primer { @Override public void primeCredentialsAsync(Credentials credentials) { runAndPreserveStacktrace( () -> { try { credentials.getRequestMetadata(); } catch (IOException e) { throw new RuntimeException(e); } }); } DefaultPrimer(); @VisibleForTesting  DefaultPrimer(
      Consumer<String> classloaderStrategy,
      String grpcResourcePath,
      String protobufResourcePath,
      ExecutorService executorService); @Override void primeGrpcAsync(); @Override void primeProtobufAsync(); @Override void primeAllVersionsAsync(); @Override void primeCredentialsAsync(Credentials credentials);  }
@Test public void primeCredentials_requestsMetadata() throws IOException { new DefaultPrimer(classloaderStrategy, "not used", "not used", DIRECT_EXECUTOR) .primeCredentialsAsync(credentials); verify(credentials).getRequestMetadata(); }