private static void testInvocation0(String path) throws IOException, ParseException {
        try (CloseableHttpClient hc = HttpClients.createMinimal()) {
            final HttpPost req = new HttpPost(server.httpUri().resolve(path));
            req.setEntity(new StringEntity("Hello, world!", StandardCharsets.UTF_8));

            try (CloseableHttpResponse res = hc.execute(req)) {
                assertThat(res.getCode()).isEqualTo(200);
                assertThat(EntityUtils.toString(res.getEntity())).isEqualTo("Hello, world!");
            }
        }
    }
Ensures that the {@link Server} is always started when a test begins. This is necessary even if we
enabled auto-start for {@link ServerRule} because we stop it in {@link #testStartStop()}.
core/src/test/java/com/linecorp/armeria/server/ServerTest.java