@CsvSource({
            "0,     10000, 10000",
            "15000, 20000, 0",
            "20000, 15000, 15000",
    })
    @ParameterizedTest
    void pingIntervalShouldBeLessThanIdleTimeout(long idleTimeoutMillis, long pingIntervalMillis,
                                                 long expectedPingIntervalMillis) {
        final ServerConfig config = newServerWithKeepAlive(idleTimeoutMillis, pingIntervalMillis).config();
        assertThat(config.idleTimeoutMillis()).isEqualTo(idleTimeoutMillis);
        assertThat(config.pingIntervalMillis()).isEqualTo(expectedPingIntervalMillis);
    }
Makes sure that {@link ServerBuilder#decorator(DecoratingHttpServiceFunction)} works at every service and
virtual hosts and {@link VirtualHostBuilder#decorator(DecoratingHttpServiceFunction)} works only at
its own services.
core/src/test/java/com/linecorp/armeria/server/ServerBuilderTest.java