public async Task AddHeader()
        {
            var handler = Handlers.Default.Then(Handlers.Header("header-name", "old-value"))
                          .Then(Handlers.AddHeader("header-name", "new-value"));

            await WithServerAndClient(handler, async (server, client) =>
            {
                var resp = await client.GetAsync(server.Uri);
                AssertHeader(resp, "header-name", "old-value", "new-value");
            });
        }
        public async Task ChainStatusAndHeadersAndBody()
        {
            var handler = Handlers.Status(201)
                          .Then(Handlers.Header("name1", "value1"))
                          .Then(Handlers.Header("name2", "value2"))
                          .Then(Handlers.BodyString("text/plain", "hello"));

            await WithServerAndClient(handler, async (server, client) =>
            {
                var resp = await client.GetAsync(server.Uri);
                Assert.Equal(201, (int)resp.StatusCode);
                AssertHeader(resp, "name1", "value1");
                AssertHeader(resp, "name2", "value2");
                AssertHeader(resp, "content-type", "text/plain");
                Assert.Equal("hello", await resp.Content.ReadAsStringAsync());
            });
        }