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May 20th 2020
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go-vcr simplifies testing by recording your HTTP interactions and replaying them in future runs in order to provide fast, deterministic and accurate testing of your code.

go-vcr was inspired by the VCR library for Ruby.


Install go-vcr by executing the command below:

$ go get


Here is a simple example of recording and replaying etcd HTTP interactions.

You can find other examples in the example directory of this repository as well.

package main

import (



func main() {
	// Start our recorder
	r, err := recorder.New("fixtures/etcd")
	if err != nil {
	defer r.Stop() // Make sure recorder is stopped once done with it

	// Create an etcd configuration using our transport
	cfg := client.Config{
		Endpoints:               []string{""},
		HeaderTimeoutPerRequest: time.Second,
		Transport:               r, // Inject as transport!

	// Create an etcd client using the above configuration
	c, err := client.New(cfg)
	if err != nil {
		log.Fatalf("Failed to create etcd client: %s", err)

	// Get an example key from etcd
	etcdKey := "/foo"
	kapi := client.NewKeysAPI(c)
	resp, err := kapi.Get(context.Background(), etcdKey, nil)

	if err != nil {
		log.Fatalf("Failed to get etcd key %s: %s", etcdKey, err)

	log.Printf("Successfully retrieved etcd key %s: %s", etcdKey, resp.Node.Value)

Custom Request Matching

During replay mode, You can customize the way incoming requests are matched against the recorded request/response pairs by defining a Matcher function. For example, the following matcher will match on method, URL and body:

r, err := recorder.New("fixtures/matchers")
if err != nil {
defer r.Stop() // Make sure recorder is stopped once done with it

r.SetMatcher(func(r *http.Request, i cassette.Request) bool {
	if r.Body == nil {
		return cassette.DefaultMatcher(r, i)
	var b bytes.Buffer
	if _, err := b.ReadFrom(r.Body); err != nil {
		return false
	r.Body = ioutil.NopCloser(&b)
	return cassette.DefaultMatcher(r, i) && (b.String() == "" || b.String() == i.Body)

Protecting Sensitive Data

You often provide sensitive data, such as API credentials, when making requests against a service. By default, this data will be stored in the recorded data but you probably don’t want this. Removing or replacing data before it is stored can be done by adding one or more Filters to your Recorder. Here is an example that removes the Authorization header from all requests:

r, err := recorder.New("fixtures/filters")
if err != nil {
defer r.Stop() // Make sure recorder is stopped once done with it

// Add a filter which removes Authorization headers from all requests:
r.AddFilter(func(i *cassette.Interaction) error {
    delete(i.Request.Headers, "Authorization")
    return nil


go-vcr is Open Source and licensed under the BSD License