@Test
    void sendsTimeoutHeader() {
        final long configuredTimeoutMinutes = 100;
        final TestServiceBlockingStub stub =
                Clients.newDerivedClient(
                        blockingStub,
                        ClientOptions.RESPONSE_TIMEOUT_MILLIS.newValue(
                                TimeUnit.MINUTES.toMillis(configuredTimeoutMinutes)));
        stub.emptyCall(EMPTY);
        final long transferredTimeoutMinutes = TimeUnit.NANOSECONDS.toMinutes(
                TimeoutHeaderUtil.fromHeaderValue(
                        CLIENT_HEADERS_CAPTURE.get().get(GrpcHeaderNames.GRPC_TIMEOUT)));
        assertThat(transferredTimeoutMinutes).isEqualTo(configuredTimeoutMinutes);
    }
Must be at least {@link #unaryPayloadLength()}, plus some to account for encoding overhead.
grpc/src/test/java/com/linecorp/armeria/client/grpc/GrpcClientTest.java