func assertMD5(t *testing.T, req *request.Request) {
err := req.Build()
assert.NoError(t, err)
b, _ := ioutil.ReadAll(req.HTTPRequest.Body)
out := md5.Sum(b)
assert.NotEmpty(t, b)
assert.Equal(t, base64.StdEncoding.EncodeToString(out[:]), req.HTTPRequest.Header.Get("Content-MD5"))
}