Fake Unleash for Go

[unleash]

Fake Unleash for Go

[jrbarron]

@apexskier Feature is now public on the v3 branch actually after we added the ListFeatures() function. I wrote a quick hacky version of a FakeUnleash for someone so I can share that here. It creates a fake server instead of mocking the client so might not be what you are looking for, but maybe it helps:

package unleash

import (
	"encoding/json"
	"github.com/Unleash/unleash-client-go/v3/api"
	"net/http"
	"net/http/httptest"
	"sync"
	"time"
)

type FakeUnleashServer struct {
	sync.RWMutex
	srv      *httptest.Server
	features map[string]bool
}

func (f *FakeUnleashServer) Url() string {
	return f.srv.URL
}

func (f *FakeUnleashServer) Enable(feature string) {
	f.setEnabled(feature, true)
}

func (f *FakeUnleashServer) Disable(feature string) {
	f.setEnabled(feature, false)
}

func (f *FakeUnleashServer) setEnabled(feature string, enabled bool) {
	f.Lock()
	wasEnabled := f.features[feature]
	if enabled != wasEnabled {
		f.features[feature] = enabled
	}
	f.Unlock()
}

func (f *FakeUnleashServer) IsEnabled(feature string) bool {
	f.RLock()
	enabled := f.features[feature]
	f.RUnlock()
	return enabled
}

func (f *FakeUnleashServer) setAll(enabled bool) {
	for k := range f.features {
		f.setEnabled(k, enabled)
	}
}

func (f *FakeUnleashServer) EnableAll() {
	f.setAll(true)
}

func (f *FakeUnleashServer) DisableAll() {
	f.setAll(false)
}

func (f *FakeUnleashServer) handler(w http.ResponseWriter, req *http.Request) {
	switch req.Method + " " + req.URL.Path {
	case "GET /client/features":

		features := []api.Feature{}
		for k, v := range f.features {
			features = append(features, api.Feature{
				Name:    k,
				Enabled: v,
				Strategies: []api.Strategy{
					{
						Id:   0,
						Name: "default",
					},
				},
				CreatedAt: time.Time{},
			})
		}

		res := api.FeatureResponse{
			Response: api.Response{Version: 2},
			Features: features,
		}
		dec := json.NewEncoder(w)
		if err := dec.Encode(res); err != nil {
			println(err.Error())
		}
	case "POST /client/register":
		fallthrough
	case "POST /client/metrics":
		w.WriteHeader(200)
	default:
		w.Write([]byte("Unknown route"))
		w.WriteHeader(500)
	}
}

func NewFakeUnleash() *FakeUnleashServer {
	faker := &FakeUnleashServer{
		features: map[string]bool{},
	}
	faker.srv = httptest.NewServer(http.HandlerFunc(faker.handler))
	return faker
}

The way it works is that you create call NewFakeUnleash() to get an instance of the fake server and pass the URL of this server to your unleash client. You then toggle features on the server by calling Enable() and Disable().

[jrbarron]

@yofriadi I'm not sure what you mean by not compatible 🤔

Here's a quick example of configuring your client to talk to the fake server:

func TestFakeUnleashServer(t *testing.T) {
	faker := unleash.NewFakeUnleash()

	unleash.Initialize(
		unleash.WithListener(&unleash.DebugListener{}),
		unleash.WithAppName("my-application"),
		unleash.WithUrl(faker.Url()),
		unleash.WithRefreshInterval(1*time.Millisecond),
	)
	unleash.WaitForReady()

	faker.Enable("foo")
	<-time.After(5 * time.Millisecond) // wait until client refreshes

	if unleash.IsEnabled("foo") != true {
		t.Errorf("expected IsEnabled to be true")
	}

	faker.Disable("foo")
	<-time.After(5 * time.Millisecond) // wait until client refreshes

	if unleash.IsEnabled("foo") != false {
		t.Errorf("expected IsEnabled to be false")
	}
}

[ivarconr]

That would be nice. What do you think @jrbarron ?

[jrbarron]

This is the first I've heard of it so no plans yet, but it sounds like a good idea. This will probably involve some refactoring internally since both the repository and the metrics stuff should be abstracted into interfaces so we can stub out the network behavior.

I haven't had much free time lately and the time I have spent on Unleash has been adding support for v4 and variants so if someone else would like to take a stab at this, they are certainly welcome. Otherwise I will try to find some time after I finish the v4 changes.

[jrmullins]

Thanks for the feedback. Do you guys have any recommendations on unit testing in general? Do you guys set up an httptest handler's to mock unleash responses?

[jrbarron]

@jrmullins I have used a library called gock for mocking the http traffic in the Unleash.

[apexskier]

From my perspective, the easiest way to make this package mockable would be to allow defining a custom storage implementation that we can mock the results of. WithStorage is already public, but it's not usable because the repository requires it's return data to be of type api.Feature, which is in an internal package and can't be used by consumers. If Feature was public, this would be much easier.

https://play.golang.org/p/KIr8rYKTjUD

[apexskier]

@jrbarron Thanks! This ended up allowing us to mock unleash in tests; everything's working well now.

[yofriadi]

hi @jrbarron could we have some example implementation for mocking using FakeUnleashServer

because as far as I can try, type FakeUnleashServer is not compatible with type unleash.Client, or maybe I am missing something here, thankyou