Firestore firestore = FirestoreOptions.getDefaultInstance()
    .toBuilder()
    .setProjectId(Config.PROJECT_ID)
    .setHost("localhost:9000")
    .setChannelProvider(
      InstantiatingGrpcChannelProvider.newBuilder().setEndpoint(Config.FIRESTORE_EMULATOR_URL)
        .setChannelConfigurator(input -> {
          input.usePlaintext();
          return input;
        }).build())
    .setCredentialsProvider(FixedCredentialsProvider.create(new FakeCredentials()))
    .setCredentials(new FakeCredentials())
    .setHeaderProvider(() -> ImmutableMap.of("Authorization", "Bearer owner"))
    .build().getService();

firestore.collection("mycollection").listDocuments();


    public static class FakeCredentials extends Credentials {
        private final Map<String, List<String>> HEADERS =
                ImmutableMap.of("Authorization", Arrays.asList("Bearer owner"));

        @Override
        public String getAuthenticationType() {
            throw new IllegalArgumentException("Not supported");
        }

        @Override
        public Map<String, List<String>> getRequestMetadata(URI uri) {
            return HEADERS;
        }

        @Override
        public boolean hasRequestMetadata() {
            return true;
        }

        @Override
        public boolean hasRequestMetadataOnly() {
            return true;
        }

        @Override
        public void refresh() {
        }
    }