@GetMapping(value = "/{id}")
    public Mono<Post> get(@PathVariable(value = "id") Long id) {
        return this.posts.findById(id);
    }
@Test
    public void getAllPostsWillBeOk() throws Exception {
        this.rest
            .get()
            .uri("/posts")
            .accept(APPLICATION_JSON)
            .exchange()
            .expectBody()
            .jsonPath("$.length()")
            .isEqualTo(2);
    }