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 -v gopkg.in/dnaeon/go-vcr.v3/recorderNote, that if you are migrating from a previous version of go-vcr,
you need re-create your test cassettes, because as of go-vcr v3
there is a new format of the cassette, which is not
backwards-compatible with older releases.
Please check the examples from this repo for example
usage of go-vcr.
You can also refer to the test cases for additional examples.
During replay mode, You can customize the way incoming requests are
matched against the recorded request/response pairs by defining a
MatcherFunc function.
For example, the following matcher will match on method, URL and body:
func customMatcher(r *http.Request, i Request) bool {
if r.Body == nil || r.Body == http.NoBody {
return cassette.DefaultMatcher(r, i)
}
var reqBody []byte
var err error
reqBody, err = ioutil.ReadAll(r.Body)
if err != nil {
log.Fatal("failed to read request body")
}
r.Body.Close()
r.Body = ioutil.NopCloser(bytes.NewBuffer(reqBody))
return r.Method == i.Method && r.URL.String() == i.URL && string(reqBody) == i.Body
}
func recorderWithCustomMatcher() {
rec, err := recorder.New("fixtures/matchers")
if err != nil {
log.Fatal(err)
}
defer rec.Stop() // Make sure recorder is stopped once done with it
rec.SetReplayableInteractions(true)
rec.SetMatcher(customMatcher)
client := rec.GetDefaultClient()
resp, err := client.Get("https://www.google.com/")
...
...
...
}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 {
log.Fatal(err)
}
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
})Filters added using *Recorder.AddFilter are applied within VCR's
custom http.Transport. This means that if you edit a response in
such a filter then subsequent test code will see the edited
response. This may not be desirable in all cases.
For instance, if a response body contains an OAuth access token that
is needed for subsequent requests, then redacting the access token in
Filter will result in authorization failures.
Another way to edit recorded interactions is to use
PreSaveFilter. Filters added with this method are applied just
before interactions are saved when Recorder.Stop() is called.
r, err := recorder.New("fixtures/filters")
if err != nil {
log.Fatal(err)
}
defer r.Stop() // Make sure recorder is stopped once done with it
// Your test code will continue to see the real access token and
// it is redacted before the recorded interactions are saved on disk
r.AddSaveFilter(func(i *cassette.Interaction) error {
if strings.Contains(i.URL, "/oauth/token") {
i.Response.Body = `{"access_token": "[REDACTED]"}`
}
return nil
})Sometimes you want to allow specific requests to pass through to the remote server without recording anything.
Globally, you can use ModePassthrough for this, but if you want to
disable the recorder for individual requests, you can add
Passthrough handlers to the recorder.
The function takes a pointer to the original request, and returns a boolean, indicating if the request should pass through to the remote server.
Here's an example to pass through requests to a specific endpoint:
// Passthrough the request to the remote server if the path matches "/login".
r.AddPassthrough(func(req *http.Request) bool {
return req.URL.Path == "/login"
})go-vcr is Open Source and licensed under the
BSD License