diff --git a/README.md b/README.md
index a447342..f52a206 100644
--- a/README.md
+++ b/README.md
@@ -52,7 +52,8 @@ open Lwt.Infix
 
 module Make (HTTP_client : Http_mirage_client.S) = struct
   let start http_client =
-    Http_mirage_client.one_request http_client "https://mirage.io/"
+    let body_f _response acc data = Lwt.return (acc ^ data) in
+    Http_mirage_client.one_request http_client "https://mirage.io/" body_f ""
     >>= function
     | Ok (resp, body) -> ...
     | Error _ -> ...
diff --git a/src/http_mirage_client.ml b/src/http_mirage_client.ml
index 1938e28..97c6669 100644
--- a/src/http_mirage_client.ml
+++ b/src/http_mirage_client.ml
@@ -153,7 +153,8 @@ let prepare_http_1_1_headers headers host user_pass body_length =
     | Some v -> add headers "content-length" (string_of_int v) in
   add_authentication ~add headers user_pass
 
-let single_http_1_1_request ?config flow user_pass host meth path headers body =
+let single_http_1_1_request
+    ?config flow user_pass host meth path headers body f f_init =
   let body_length = Option.map String.length body in
   let headers = prepare_http_1_1_headers headers host user_pass body_length in
   let req = Httpaf.Request.create ~headers meth path in
@@ -163,34 +164,26 @@ let single_http_1_1_request ?config flow user_pass host meth path headers body =
     fun v ->
       if not !w then Lwt.wakeup_later notify_finished v
       ; w := true in
+  let on_eof response data () = wakeup (Ok (response, data)) in
   let response_handler response body =
-    let buf = Buffer.create 0x100 in
-    let rec on_eof () =
-      let response =
-        {
-          version= response.Httpaf.Response.version
-        ; status= (response.Httpaf.Response.status :> H2.Status.t)
-        ; reason= response.Httpaf.Response.reason
-        ; headers=
-            H2.Headers.of_list
-              (Httpaf.Headers.to_list response.Httpaf.Response.headers)
-        } in
-      wakeup (Ok (response, Some (Buffer.contents buf)))
-    and on_read ba ~off ~len =
-      Buffer.add_string buf (Bigstringaf.substring ~off ~len ba)
-      ; Httpaf.Body.schedule_read body ~on_read ~on_eof in
-    let on_eof () =
-      let response =
-        {
-          version= response.Httpaf.Response.version
-        ; status= (response.Httpaf.Response.status :> H2.Status.t)
-        ; reason= response.Httpaf.Response.reason
-        ; headers=
-            H2.Headers.of_list
-              (Httpaf.Headers.to_list response.Httpaf.Response.headers)
-        } in
-      wakeup (Ok (response, None)) in
-    Httpaf.Body.schedule_read body ~on_read ~on_eof in
+    let response =
+      {
+        version= response.Httpaf.Response.version
+      ; status= (response.Httpaf.Response.status :> H2.Status.t)
+      ; reason= response.Httpaf.Response.reason
+      ; headers=
+          H2.Headers.of_list
+            (Httpaf.Headers.to_list response.Httpaf.Response.headers)
+      } in
+    let rec on_read on_eof acc ba ~off ~len =
+      let acc =
+        acc >>= fun acc -> f response acc (Bigstringaf.substring ~off ~len ba)
+      in
+      Httpaf.Body.schedule_read body ~on_read:(on_read on_eof acc)
+        ~on_eof:(on_eof response acc) in
+    let f_init = Lwt.return f_init in
+    Httpaf.Body.schedule_read body ~on_read:(on_read on_eof f_init)
+      ~on_eof:(on_eof response f_init) in
   let error_handler e =
     let err =
       match e with
@@ -216,8 +209,8 @@ let prepare_h2_headers headers host user_pass body_length =
       (string_of_int (Option.value ~default:0 body_length)) in
   add_authentication ~add headers user_pass
 
-let single_h2_request ?config ~scheme flow user_pass host meth path headers body
-    =
+let single_h2_request
+    ?config ~scheme flow user_pass host meth path headers body f f_init =
   let body_length = Option.map String.length body in
   let headers = prepare_h2_headers headers host user_pass body_length in
   let req = H2.Request.create ~scheme ~headers meth path in
@@ -227,30 +220,24 @@ let single_h2_request ?config ~scheme flow user_pass host meth path headers body
     fun v ->
       if not !w then Lwt.wakeup_later notify_finished v
       ; w := true in
+  let on_eof response data () = wakeup (Ok (response, data)) in
   let response_handler response response_body =
-    let buf = Buffer.create 0x100 in
-    let rec on_eof () =
-      let response =
-        {
-          version= {major= 2; minor= 0}
-        ; status= response.H2.Response.status
-        ; reason= ""
-        ; headers= response.H2.Response.headers
-        } in
-      wakeup (Ok (response, Some (Buffer.contents buf)))
-    and on_read ba ~off ~len =
-      Buffer.add_string buf (Bigstringaf.substring ~off ~len ba)
-      ; H2.Body.Reader.schedule_read response_body ~on_read ~on_eof in
-    let on_eof () =
-      let response =
-        {
-          version= {major= 2; minor= 0}
-        ; status= response.H2.Response.status
-        ; reason= ""
-        ; headers= response.H2.Response.headers
-        } in
-      wakeup (Ok (response, None)) in
-    H2.Body.Reader.schedule_read response_body ~on_read ~on_eof in
+    let response =
+      {
+        version= {major= 2; minor= 0}
+      ; status= response.H2.Response.status
+      ; reason= ""
+      ; headers= response.H2.Response.headers
+      } in
+    let rec on_read on_eof acc ba ~off ~len =
+      let acc =
+        acc >>= fun acc -> f response acc (Bigstringaf.substring ~off ~len ba)
+      in
+      H2.Body.Reader.schedule_read response_body ~on_read:(on_read on_eof acc)
+        ~on_eof:(on_eof response acc) in
+    let f_init = Lwt.return f_init in
+    H2.Body.Reader.schedule_read response_body ~on_read:(on_read on_eof f_init)
+      ~on_eof:(on_eof response f_init) in
   let error_handler e =
     let err =
       match e with
@@ -319,7 +306,8 @@ let alpn_protocol_of_string = function
   | "h2" -> Some `H2
   | _ -> None
 
-let single_request ~ctx ~alpn_protocol ?config cfg ~meth ~headers ?body uri =
+let single_request
+    ~ctx ~alpn_protocol ?config cfg ~meth ~headers ?body uri f f_init =
   Lwt.return (decode_uri ~ctx uri)
   >>? fun (ctx, scheme, host, user_pass, path) ->
   let ctx =
@@ -333,19 +321,26 @@ let single_request ~ctx ~alpn_protocol ?config cfg ~meth ~headers ?body uri =
   Mimic.resolve ctx >>? fun flow ->
   (match Option.bind (alpn_protocol flow) alpn_protocol_of_string, config with
   | (Some `HTTP_1_1 | None), Some (`HTTP_1_1 config) ->
-    single_http_1_1_request ~config flow user_pass host meth path headers body
+    single_http_1_1_request ~config flow user_pass host meth path headers body f
+      f_init
   | (Some `HTTP_1_1 | None), None ->
-    single_http_1_1_request flow user_pass host meth path headers body
+    single_http_1_1_request flow user_pass host meth path headers body f f_init
   | (Some `H2 | None), Some (`H2 config) ->
     single_h2_request ~config ~scheme flow user_pass host meth path headers body
+      f f_init
   | Some `H2, None ->
-    single_h2_request ~scheme flow user_pass host meth path headers body
+    single_h2_request ~scheme flow user_pass host meth path headers body f
+      f_init
   | Some `H2, Some (`HTTP_1_1 _) ->
-    single_h2_request ~scheme flow user_pass host meth path headers body
+    single_h2_request ~scheme flow user_pass host meth path headers body f
+      f_init
   | Some `HTTP_1_1, Some (`H2 _) ->
-    single_http_1_1_request flow user_pass host meth path headers body)
+    single_http_1_1_request flow user_pass host meth path headers body f f_init)
   >>= fun r ->
-  Mimic.close flow >|= fun () -> r
+  Mimic.close flow >>= fun () ->
+  match r with
+  | Error _ as e -> Lwt.return e
+  | Ok (resp, body) -> Lwt.map (fun body -> Ok (resp, body)) body
 
 let tls_config ?tls_config ?config authenticator user's_authenticator =
   lazy
@@ -378,7 +373,7 @@ let resolve_location ~uri ~location =
     | _ -> Error (`Msg ("expected an absolute uri, got: " ^ uri)))
   | _ -> Error (`Msg ("unknown location (relative path): " ^ location))
 
-let one_request
+let request
     ?config
     ?tls_config:cfg
     {ctx; alpn_protocol; authenticator}
@@ -388,18 +383,20 @@ let one_request
     ?body
     ?(max_redirect = 5)
     ?(follow_redirect = true)
-    uri =
+    uri
+    f
+    f_init =
   let tls_config =
     tls_config ?tls_config:cfg ?config authenticator user's_authenticator in
   if not follow_redirect then
     single_request ~ctx ~alpn_protocol ?config tls_config ~meth ~headers ?body
-      uri
+      uri f f_init
   else
     let rec follow_redirect count uri =
       if count = 0 then Lwt.return_error (`Msg "Redirect limit exceeded")
       else
         single_request ~ctx ~alpn_protocol ?config tls_config ~meth ~headers
-          ?body uri
+          ?body uri f f_init
         >>? fun (resp, body) ->
         if Status.is_redirection resp.status then
           match Headers.get resp.headers "location" with
diff --git a/src/http_mirage_client.mli b/src/http_mirage_client.mli
index 2baf154..f0ef229 100644
--- a/src/http_mirage_client.mli
+++ b/src/http_mirage_client.mli
@@ -22,7 +22,7 @@ type response = {
   ; headers: Headers.t
 }
 
-val one_request :
+val request :
      ?config:[ `H2 of H2.Config.t | `HTTP_1_1 of Httpaf.Config.t ]
   -> ?tls_config:Tls.Config.client
   -> t
@@ -33,4 +33,11 @@ val one_request :
   -> ?max_redirect:int
   -> ?follow_redirect:bool
   -> string
-  -> (response * string option, [> Mimic.error ]) result Lwt.t
+  -> (response -> 'a -> string -> 'a Lwt.t)
+  -> 'a
+  -> (response * 'a, [> Mimic.error ]) result Lwt.t
+(** [request ~config ~tls_config t ~authenticator ~meth ~headers ~body
+     ~max_redirect ~follow_redirect url body_f body_init] does a HTTP request
+    to [url] using [meth] and the HTTP protocol in [config]. The response is
+    the value of this function. The body is provided in chunks (see [body_f]).
+    Reasonably defaults are used if not provided. *)
diff --git a/test/dune b/test/dune
new file mode 100644
index 0000000..09e6f9e
--- /dev/null
+++ b/test/dune
@@ -0,0 +1,10 @@
+(executable
+ (name test)
+ (libraries http-mirage-client tcpip.stack-socket paf.mirage
+   mirage-clock-unix mirage-random-stdlib happy-eyeballs-lwt mirage-time-unix
+   mimic-happy-eyeballs alcotest-lwt))
+
+(rule
+ (alias runtest)
+ (action
+  (run ./test.exe --color=always)))
diff --git a/test/test.ml b/test/test.ml
new file mode 100644
index 0000000..508ecd0
--- /dev/null
+++ b/test/test.ml
@@ -0,0 +1,167 @@
+(* Functoria *)
+
+module DNS_client = Dns_client_mirage.Make (Mirage_random_stdlib) (Time) (Mclock) (Pclock) (Tcpip_stack_socket.V4V6)
+module Happy_eyeballs = Happy_eyeballs_mirage.Make (Time) (Mclock) (Tcpip_stack_socket.V4V6) (DNS_client)
+module Mimic_happy_eyeballs = Mimic_happy_eyeballs.Make (Tcpip_stack_socket.V4V6) (DNS_client) (Happy_eyeballs)
+module HTTP_server = Paf_mirage.Make (Tcpip_stack_socket.V4V6.TCP)
+module HTTP_client = Http_mirage_client.Make (Pclock) (Tcpip_stack_socket.V4V6.TCP) (Mimic_happy_eyeballs)
+
+let http_1_1_error_handler ?notify (ipaddr, port) ?request:_ error respond =
+  let contents = match error with
+    | `Bad_gateway -> Fmt.str "Bad gateway (%a:%d)" Ipaddr.pp ipaddr port
+    | `Bad_request -> Fmt.str "Bad request (%a:%d)" Ipaddr.pp ipaddr port
+    | `Exn exn -> Fmt.str "Exception %S (%a:%d)" (Printexc.to_string exn) Ipaddr.pp ipaddr port
+    | `Internal_server_error -> Fmt.str "Internal server error (%a:%d)" Ipaddr.pp ipaddr port in
+  let open Httpaf in
+  Option.iter (fun push -> push (Some ((ipaddr, port), error))) notify ;
+  let headers = Headers.of_list
+    [ "content-type", "text/plain"
+    ; "content-length", string_of_int (String.length contents)
+    ; "connection", "close" ] in
+  let body = respond headers in
+  Body.write_string body contents ;
+  Body.close_writer body
+
+let alpn_error_handler
+  : type reqd headers request response ro wo.
+    ?notify:(((Ipaddr.t * int) * Alpn.server_error) option -> unit) ->
+    (Ipaddr.t * int) -> (reqd, headers, request, response, ro, wo) Alpn.protocol ->
+    ?request:request -> Alpn.server_error -> (headers -> wo) -> unit
+  = fun ?notify (ipaddr, port) protocol ?request:_ error respond ->
+    let contents = match error with
+      | `Bad_gateway -> Fmt.str "Bad gateway (%a:%d)" Ipaddr.pp ipaddr port
+      | `Bad_request -> Fmt.str "Bad request (%a:%d)" Ipaddr.pp ipaddr port
+      | `Exn exn -> Fmt.str "Exception %S (%a:%d)" (Printexc.to_string exn) Ipaddr.pp ipaddr port
+      | `Internal_server_error -> Fmt.str "Internal server error (%a:%d)" Ipaddr.pp ipaddr port in
+    Option.iter (fun push -> push (Some ((ipaddr, port), error))) notify ;
+    let headers =
+      [ "content-type", "text/plain"
+      ; "content-length", string_of_int (String.length contents) ] in
+    match protocol with
+    | Alpn.HTTP_1_1 _ ->
+      let open Httpaf in
+      let headers = Headers.of_list (("connection", "close") :: headers) in
+      let body = respond headers in
+      Body.write_string body contents ;
+      Body.close_writer body
+    | Alpn.H2 _ ->
+      let open H2 in
+      let headers = Headers.of_list headers in
+      let body = respond headers in
+      H2.Body.Writer.write_string body contents ;
+      H2.Body.Writer.close body
+
+type alpn_handler =
+   { handler : 'reqd 'headers 'request 'response 'ro 'wo.
+     'reqd -> ('reqd, 'headers, 'request, 'response, 'ro, 'wo) Alpn.protocol -> unit }
+[@@unboxed]
+
+let server ?error ?stop stack = function
+  | `HTTP_1_1 (port, handler) ->
+    let open Lwt.Syntax in
+    let+ http_server = HTTP_server.init ~port stack in
+    let http_service = HTTP_server.http_service ~error_handler:(http_1_1_error_handler ?notify:error)
+      (fun _flow (_ipaddr, _port) -> handler) in
+    HTTP_server.serve ?stop http_service http_server
+  | `ALPN (tls, port, handler) ->
+    let open Lwt.Syntax in
+    let alpn_handler =
+      { Alpn.error= (fun edn protocol ?request v respond -> alpn_error_handler ?notify:error edn protocol ?request v respond)
+      ; Alpn.request= (fun _flow (_ipaddr, _port) reqd protocol -> handler.handler reqd protocol) } in
+    let+ http_server = HTTP_server.init ~port stack in
+    let alpn_service = HTTP_server.alpn_service ~tls alpn_handler in
+    HTTP_server.serve ?stop alpn_service http_server
+
+let stack ipaddr =
+  let open Lwt.Syntax in
+  let* tcpv4v6 = Tcpip_stack_socket.V4V6.TCP.connect ~ipv4_only:false ~ipv6_only:false
+    ipaddr None in
+  let* udpv4v6 = Tcpip_stack_socket.V4V6.UDP.connect ~ipv4_only:false ~ipv6_only:false
+    ipaddr None in
+  Tcpip_stack_socket.V4V6.connect udpv4v6 tcpv4v6
+
+let test01 =
+  Alcotest_lwt.test_case "Simple Hello World! (GET)" `Quick @@ fun _sw () ->
+  let open Lwt.Syntax in
+  let stop = Lwt_switch.create () in
+  let handler reqd =
+    let open Httpaf in
+    let contents = "Hello World!" in
+    let headers = Headers.of_list
+      [ "content-type", "text/plain"
+      ; "content-length", string_of_int (String.length contents)
+      ; "connection", "close" ] in
+    let response = Response.create ~headers `OK in
+    Reqd.respond_with_string reqd response contents in
+  let* stack = stack Ipaddr.V4.Prefix.loopback in
+  let happy_eyeballs = Happy_eyeballs.create stack in
+  let* ctx = Mimic_happy_eyeballs.connect happy_eyeballs in
+  let* t = HTTP_client.connect ctx in
+  let* `Initialized _thread = server ~stop (Tcpip_stack_socket.V4V6.tcp stack)
+    (`HTTP_1_1 (8080, handler)) in
+  let* result = Http_mirage_client.request t "http://localhost:8080/"
+    (fun _response buf str -> Buffer.add_string buf str ; Lwt.return buf)
+    (Buffer.create 0x100) in
+  match result with
+  | Error err ->
+    let* () = Lwt_switch.turn_off stop in
+    let* () = Tcpip_stack_socket.V4V6.disconnect stack in
+    Alcotest.failf "Client error: %a" Mimic.pp_error err
+  | Ok (_response, buf) ->
+    let* () = Lwt_switch.turn_off stop in
+    let* () = Tcpip_stack_socket.V4V6.disconnect stack in
+    let body = Buffer.contents buf in
+    Alcotest.(check string) "body" "Hello World!" body ;
+    Lwt.return_unit
+
+let random_string ~len =
+  let res = Bytes.create len in
+  for i = 0 to len - 1 do
+    Bytes.set res i (Char.chr (Random.bits () land 0xff))
+  done ; Bytes.unsafe_to_string res
+
+let test02 =
+  Alcotest_lwt.test_case "Repeat (POST)" `Quick @@ fun _sw () ->
+  let open Lwt.Syntax in
+  let stop = Lwt_switch.create () in
+  let handler reqd =
+    let open Httpaf in
+    let { Request.meth; _ } = Reqd.request reqd in
+    if meth <> `POST then invalid_arg "Invalid HTTP method" ;
+    let headers = Headers.of_list
+      [ "content-type", "text/plain" ] in
+    let response = Response.create ~headers `OK in
+    let src = Reqd.request_body reqd in
+    let dst = Reqd.respond_with_streaming reqd response in
+    let rec on_eof () =
+      Body.close_reader src ;
+      Body.close_writer dst
+    and on_read buf ~off ~len =
+      Body.write_bigstring dst ~off ~len buf ;
+      Body.schedule_read src ~on_eof ~on_read in
+    Body.schedule_read src ~on_eof ~on_read in
+  let* stack = stack Ipaddr.V4.Prefix.loopback in
+  let happy_eyeballs = Happy_eyeballs.create stack in
+  let* ctx = Mimic_happy_eyeballs.connect happy_eyeballs in
+  let* t = HTTP_client.connect ctx in
+  let* `Initialized _thread = server ~stop (Tcpip_stack_socket.V4V6.tcp stack)
+    (`HTTP_1_1 (8080, handler)) in
+  let str = random_string ~len:0x1000 in
+  let* result = Http_mirage_client.request ~meth:`POST ~body:str t "http://localhost:8080/"
+    (fun _response buf str -> Buffer.add_string buf str ; Lwt.return buf)
+    (Buffer.create 0x1000) in
+  match result with
+  | Error err ->
+    let* () = Lwt_switch.turn_off stop in
+    let* () = Tcpip_stack_socket.V4V6.disconnect stack in
+    Alcotest.failf "Client error: %a" Mimic.pp_error err
+  | Ok (_response, buf) ->
+    let* () = Lwt_switch.turn_off stop in
+    let* () = Tcpip_stack_socket.V4V6.disconnect stack in
+    let body = Buffer.contents buf in
+    Alcotest.(check string) "body" str body ;
+    Lwt.return_unit
+ 
+ let () = Alcotest_lwt.run "http-mirage-client"
+     [ "http/1.1", [ test01; test02 ] ]
+   |> Lwt_main.run