ExVCR
Record and replay HTTP interactions library for elixir. It's inspired by Ruby's VCR (https://github.com/vcr/vcr), and trying to provide similar functionalities.
Basics
-
The following HTTP libraries can be applied.
-
HTTP interactions are recorded as JSON file.
- The JSON file can be recorded automatically (vcr_cassettes) or manually updated (custom_cassettes)
Notes
- In case test behaves unstable, please try to specify
use ExUnit.Case, async: false
.
Install
Add :exvcr
to deps
section of mix.exs
.
def deps do
[ {:exvcr, "~> 0.8", only: :test} ]
end
Optionally, preferred_cli_env: [vcr: :test]
can be specified for running mix vcr
in :test
env by default.
def project do
[ ...
preferred_cli_env: [
vcr: :test, "vcr.delete": :test, "vcr.check": :test, "vcr.show": :test
],
...
end
Usage
- Add
use ExVCR.Mock
to the test module. This mocks ibrowse by default. For using hackney, specifyadapter: ExVCR.Adapter.Hackney
options as follows.
Example with ibrowse
defmodule ExVCR.Adapter.IBrowseTest do
use ExUnit.Case, async: false
use ExVCR.Mock
setup_all do
ExVCR.Config.cassette_library_dir("fixture/vcr_cassettes")
:ok
end
test "example single request" do
use_cassette "example_ibrowse" do
:ibrowse.start
{:ok, status_code, _headers, body} = :ibrowse.send_req('http://example.com', [], :get)
assert status_code == '200'
assert to_string(body) =~ ~r/Example Domain/
end
end
test "httpotion" do
use_cassette "example_httpotion" do
HTTPotion.start
assert HTTPotion.get("http://example.com", []).body =~ ~r/Example Domain/
end
end
end
Example with hackney
defmodule ExVCR.Adapter.HackneyTest do
use ExUnit.Case, async: false
use ExVCR.Mock, adapter: ExVCR.Adapter.Hackney
setup_all do
HTTPoison.start
end
test "get request" do
use_cassette "httpoison_get" do
assert HTTPoison.get!("http://example.com").body =~ ~r/Example Domain/
end
end
end
Example with httpc
defmodule ExVCR.Adapter.HttpcTest do
use ExUnit.Case, async: false
use ExVCR.Mock, adapter: ExVCR.Adapter.Httpc
setup_all do
:inets.start
end
test "get request" do
use_cassette "example_httpc_request" do
{:ok, result} = :httpc.request('http://example.com')
{{_http_version, _status_code = 200, _reason_phrase}, _headers, body} = result
assert to_string(body) =~ ~r/Example Domain/
end
end
Custom Cassettes
You can manually define custom cassette json file for more flexible response control rather than just recoding the actual server response.
- Optional 2nd parameter of
ExVCR.Config.cassette_library_dir
method specifies the custom cassette directory. The directory is separated from vcr cassette one for avoiding mistakenly overwriting. - Adding
custom: true
option touse_cassette
macro indicates to use the custom cassette, and it just returns the pre-defined json response, instead of requesting to server.
defmodule ExVCR.MockTest do
use ExUnit.Case
import ExVCR.Mock
setup_all do
ExVCR.Config.cassette_library_dir("fixture/vcr_cassettes", "fixture/custom_cassettes")
:ok
end
test "custom with valid response" do
use_cassette "response_mocking", custom: true do
assert HTTPotion.get("http://example.com", []).body =~ ~r/Custom Response/
end
end
The custom json file format is the same as vcr cassettes.
fixture/custom_cassettes/response_mocking.json
[
{
"request": {
"url": "http://example.com"
},
"response": {
"status_code": 200,
"headers": {
"Content-Type": "text/html"
},
"body": "<h1>Custom Response</h1>"
}
}
]
Recording VCR Cassettes
Matching
ExVCR uses url parameter to match request and cassettes. The "url" parameter in the json file is taken as regexp string.
Removing Sensitive Data
ExVCR.Config.filter_sensitive_data(pattern, placeholder)
method can be used to remove sensitive data. It searches for string matches with pattern
, which is a string representing a regular expression, and replaces with placeholder
. Replacements happen both in URLs and request and response bodies.
test "replace sensitive data" do
ExVCR.Config.filter_sensitive_data("<PASSWORD>.+</PASSWORD>", "PLACEHOLDER")
use_cassette "sensitive_data" do
assert HTTPotion.get("http://something.example.com", []).body =~ ~r/PLACEHOLDER/
end
end
ExVCR.Config.filter_request_headers(header)
method can be used to remove sensitive data in the request headers. It checks if the header
is found in the request headers and blanks out it's value with ***
.
test "replace sensitive data in request header" do
ExVCR.Config.filter_request_headers("X-My-Secret-Token")
use_cassette "sensitive_data_in_request_header" do
body = HTTPoison.get!("http://localhost:34000/server?", ["X-My-Secret-Token": "my-secret-token"]).body
assert body == "test_response"
end
# The recorded cassette should contain replaced data.
cassette = File.read!("#{@dummy_cassette_dir}/sensitive_data_in_request_header.json")
assert cassette =~ "\"X-My-Secret-Token\": \"***\""
refute cassette =~ "\"X-My-Secret-Token\": \"my-secret-token\""
ExVCR.Config.filter_request_headers(nil)
end
Ignoring query params in url
If ExVCR.Config.filter_url_params(true)
is specified, query params in url will be ignored when recording cassettes.
test "filter url param flag removes url params when recording cassettes" do
ExVCR.Config.filter_url_params(true)
use_cassette "example_ignore_url_params" do
assert HTTPotion.get(
"http://localhost:34000/server?should_not_be_contained", []).body =~ ~r/test_response/
end
json = File.read!("#{__DIR__}/../#{@dummy_cassette_dir}/example_ignore_url_params.json")
refute String.contains?(json, "should_not_be_contained")
Removing headers from response
If ExVCR.Config.response_headers_blacklist(headers_blacklist)
is specified, the headers in the list will be removed from the response.
test "remove blacklisted headers" do
use_cassette "original_headers" do
assert Map.has_key?(HTTPoison.get!(@url, []).headers, "connection") == true
end
ExVCR.Config.response_headers_blacklist(["Connection"])
use_cassette "remove_blacklisted_headers" do
assert Map.has_key?(HTTPoison.get!(@url, []).headers, "connection") == false
end
ExVCR.Config.response_headers_blacklist([])
end
Clearing Mock After Each Cassette
By default, mocking through :meck.expect
is not cleared after each use_cassette
. It can cause error when mixing actual/mocking accesses. In order to clear mock, please specify [clear_mock: :true]
option through either of the followings.
# For applying all the tests under the module.
defmodule ExVCR.Adapter.OptionsTest do
use ExVCR.Mock, options: [clear_mock: true]
use ExUnit.Case, async: false
...
# For applying specific test.
use_cassette "option_clean_each", clear_mock: true do
assert HTTPotion.get(@url, []).body == "test_response1"
end
Matching Options
matching against query params
By default, query params are not used for matching. In order to include query params, specify match_requests_on: [:query]
for use_cassette
call.
test "matching query params with match_requests_on params" do
use_cassette "different_query_params", match_requests_on: [:query] do
assert HTTPotion.get("http://localhost/server?p=3", []).body =~ ~r/test_response3/
assert HTTPotion.get("http://localhost/server?p=4", []).body =~ ~r/test_response4/
end
end
matching against request body
By default, request body is not used for matching. In order to include query params, specify match_requests_on: [:request_body]
for use_cassette
call.
test "matching query params with match_requests_on params" do
use_cassette "different_request_body_params", match_requests_on: [:request_body] do
assert HTTPotion.post("http://localhost/server", [body: "p=3"]).body =~ ~r/test_response3/
assert HTTPotion.post("http://localhost/server", [body: "p=4"]).body =~ ~r/test_response4/
end
end
Default Configs
Default parameters for ExVCR.Config
module can be specified in config\config.exs
as follows.
use Mix.Config
config :exvcr, [
vcr_cassette_library_dir: "fixture/vcr_cassettes",
custom_cassette_library_dir: "fixture/custom_cassettes",
filter_sensitive_data: [
[pattern: "<PASSWORD>.+</PASSWORD>", placeholder: "PASSWORD_PLACEHOLDER"]
],
filter_url_params: false,
response_headers_blacklist: []
]
If exvcr
is defined as test-only dependency, describe the above statement in test-only config file (ex. config\test.exs
) or make it conditional (ex. wrap with if Mix.env == :test
).
Mix Tasks
The following tasks are added by including exvcr package.
[mix vcr] Show cassettes
$ mix vcr
Showing list of cassettes in [fixture/vcr_cassettes]
[File Name] [Last Update]
example_httpotion.json 2013/11/07 23:24:49
example_ibrowse.json 2013/11/07 23:24:49
example_ibrowse_multiple.json 2013/11/07 23:24:48
httpotion_delete.json 2013/11/07 23:24:47
httpotion_patch.json 2013/11/07 23:24:50
httpotion_post.json 2013/11/07 23:24:51
httpotion_put.json 2013/11/07 23:24:52
Showing list of cassettes in [fixture/custom_cassettes]
[File Name] [Last Update]
method_mocking.json 2013/10/06 22:05:38
response_mocking.json 2013/09/29 17:23:38
response_mocking_regex.json 2013/10/06 18:13:45
[mix vcr.delete] Delete cassettes
The mix vcr.delete
task deletes the cassettes that contains the specified pattern in the file name.
$ mix vcr.delete ibrowse
Deleted example_ibrowse.json.
Deleted example_ibrowse_multiple.json.
If -i (--interactive) option is specified, it asks for confirmation before deleting each file.
$ mix vcr.delete ibrowse -i
delete example_ibrowse.json? y
Deleted example_ibrowse.json.
delete example_ibrowse_multiple.json? y
Deleted example_ibrowse_multiple.json.
If -a (--all) option is specified, all the cassetes in the specified folder becomes the target for delete.
[mix vcr.check] Check cassettes
The mix vcr.check
shows how many times each cassette is applied while executing mix test
tasks. It is intended for verifying the cassettes are properly used. [Cassette Counts]
indicates the count that the pre-recorded json cassettes are applied. [Server Counts]
indicates the count that server access is performed.
$ mix vcr.check
...............................
31 tests, 0 failures
Showing hit counts of cassettes in [fixture/vcr_cassettes]
[File Name] [Cassette Counts] [Server Counts]
example_httpotion.json 1 0
example_ibrowse.json 1 0
example_ibrowse_multiple.json 2 0
httpotion_delete.json 1 0
httpotion_patch.json 1 0
httpotion_post.json 1 0
httpotion_put.json 1 0
sensitive_data.json 0 2
server1.json 0 2
server2.json 2 2
Showing hit counts of cassettes in [fixture/custom_cassettes]
[File Name] [Cassette Counts] [Server Counts]
method_mocking.json 1 0
response_mocking.json 1 0
response_mocking_regex.json 1 0
The target test file can be limited by specifying test files, as similar as mix test
tasks.
$ mix vcr.check test/exvcr_test.exs
.............
13 tests, 0 failures
Showing hit counts of cassettes in [fixture/vcr_cassettes]
[File Name] [Cassette Counts] [Server Counts]
example_httpotion.json 1 0
...
...
[mix vcr.show] Show cassettes
The mix vcr.show
task displays the contents of cassettes json file in the prettified format.
$ mix vcr.show fixture/vcr_cassettes/httpoison_get.json
[
{
"request": {
"url": "http://example.com",
"headers": [],
"method": "get",
"body": "",
"options": []
},
...
[mix vcr --help] Help
Displays helps for mix sub-tasks.
$ mix vcr --help
Usage: mix vcr [options]
Used to display the list of cassettes
-h (--help) Show helps for vcr mix tasks
-d (--dir) Specify vcr cassettes directory
-c (--custom) Specify custom cassettes directory
Usage: mix vcr.delete [options] [cassete-file-names]
Used to delete cassettes
-d (--dir) Specify vcr cassettes directory
-c (--custom) Specify custom cassettes directory
-i (--interactive) Request confirmation before attempting to delete
-a (--all) Delete all the files by ignoring specified [filenames]
Usage: mix vcr.check [options] [test-files]
Used to check cassette use on test execution
-d (--dir) Specify vcr cassettes directory
-c (--custom) Specify custom cassettes directory
Usage: mix vcr.show [cassete-file-names]
Used to show cassette contents
Notes
If the cassette save directory is changed from the default, [-d, --dir] option (for vcr cassettes) and [-c, --custom] option (for custom cassettes) can be used to specify the directory.
IEx Helper
ExVCR.IEx
module provides simple helper functions to display the http request/response in json format, instead of recording in the cassette files.
% iex -S mix
Erlang R16B03 (erts-5.10.4) ...
Interactive Elixir (0.12.5) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> require ExVCR.IEx
nil
iex(2)> ExVCR.IEx.print do
...(2)> :ibrowse.send_req('http://example.com', [], :get)
...(2)> end
[
{
"request": {
"url": "http://example.com",
"headers": [],
"method": "get",
"body": "",
"options": []
},
"response": {
"type": "ok",
"status_code": 200,
...
The adapter option can be specified as adapter
argument of print function, as follows.
% iex -S mix
Erlang R16B03 (erts-5.10.4) ...
Interactive Elixir (0.12.5) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> require ExVCR.IEx
nil
iex(2)> ExVCR.IEx.print(adapter: ExVCR.Adapter.Hackney) do
...(2)> HTTPoison.get!("http://example.com").body
...(2)> end
[
{
"request": {
"url": "http://example.com",
...
Stubbing Response
Specifing :stub
as fixture name allows directly stubbing the response header/body information based on parameter.
test "stub request works for HTTPotion" do
use_cassette :stub, [url: "http://example.com", body: "Stub Response", status_code: 200] do
response = HTTPotion.get("http://example.com", [])
assert response.body =~ ~r/Stub Response/
assert response.headers[:"Content-Type"] == "text/html"
assert response.status_code == 200
end
end
test "stub request works for HTTPoison" do
use_cassette :stub, [url: "http://www.example.com", body: "Stub Response"] do
response = HTTPoison.get!("http://www.example.com")
assert response.body =~ ~r/Stub Response/
assert response.headers["Content-Type"] == "text/html"
assert response.status_code == 200
end
end
test "stub request works for httpc" do
use_cassette :stub, [url: "http://www.example.com",
method: "get",
status_code: ["HTTP/1.1", 200, "OK"],
body: "success!"] do
{:ok, result} = :httpc.request('http://example.com')
{{_http_version, _status_code = 200, _reason_phrase}, _headers, body} = result
assert to_string(body) == "success!"
end
If the specified :url
parameter doesn't match requests called inside the use_cassette
block, it raises ExVCR.InvalidRequestError
.
The :url
can be regular expression string. Please note that you should use the ~r
sigil with /
as delimiters.
test "match URL with regular expression" do
use_cassette :stub, [url: "~r/(foo|bar)/", body: "Stub Response", status_code: 200] do
# ...
end
end
test "make sure to properly escape the /" do
# escape /path/to/file
use_cassette :stub, [url: "~r/\/path\/to\/file", body: "Stub Response", status_code: 200] do
# ...
end
end
test "the sigil delimiter cannot be anything else" do
use_cassette :stub, [url: "~r{this-delimiter-doesn-not-work}", body: "Stub Response", status_code: 200] do
# ...
end
end
TODO
- Improve performance, as it's very slow.
- Fix unstable behavior without
async: false
.