chore: export config BE handler for transformer, and unstarted http test server

testhelper/docker/resource/transformer/transformer.go

@@ -8,7 +8,7 @@ import (
 
 	"github.com/samber/lo"
 
-	dockerTestHelper "github.com/rudderlabs/rudder-go-kit/testhelper/docker"
+	dockertesthelper "github.com/rudderlabs/rudder-go-kit/testhelper/docker"
 
 	"github.com/ory/dockertest/v3"
 	"github.com/ory/dockertest/v3/docker"
@@ -56,21 +56,29 @@ func (c *config) setBackendConfigURL(url string) {
 //			})
 func WithUserTransformations(transformations map[string]string, cleaner resource.Cleaner) func(*config) {
 	return func(conf *config) {
-		backendConfigSvc := NewTestBackendConfigServer(transformations)
+		backendConfigSvc := newTestBackendConfigServer(transformations)
 
-		conf.setBackendConfigURL(dockerTestHelper.ToInternalDockerHost(backendConfigSvc.URL))
+		conf.setBackendConfigURL(dockertesthelper.ToInternalDockerHost(backendConfigSvc.URL))
 		conf.extraHosts = append(conf.extraHosts, "host.docker.internal:host-gateway")
 		cleaner.Cleanup(func() {
 			backendConfigSvc.Close()
 		})
 	}
 }
 
+// WithConnectionToHostEnabled lets transformer container connect with the host machine
+// i.e. transformer container will be able to access localhost of the host machine
+func WithConnectionToHostEnabled() func(*config) {
+	return func(conf *config) {
+		conf.extraHosts = append(conf.extraHosts, "host.docker.internal:host-gateway")
+	}
+}
+
 // WithConfigBackendURL lets transformer use custom backend config server for transformations
 // WithConfigBackendURL should not be used with WithUserTransformations option
 func WithConfigBackendURL(url string) func(*config) {
 	return func(conf *config) {
-		conf.setBackendConfigURL(url)
+		conf.setBackendConfigURL(dockertesthelper.ToInternalDockerHost(url))
 	}
 }
 

testhelper/docker/resource/transformer/transformer_backend_config.go

@@ -14,10 +14,15 @@ const (
 	versionIDKey           = "versionId"
 )
 
-func NewTestBackendConfigServer(transformations map[string]string) *kithttptest.Server {
+func newTestBackendConfigServer(transformations map[string]string) *kithttptest.Server {
+	return kithttptest.NewServer(NewTransformerBackendConfigHandler(transformations))
+}
+
+// NewTransformerBackendConfigHandler returns http request handler to handle all backend config requests by transformer
+func NewTransformerBackendConfigHandler(transformations map[string]string) http.Handler {
 	mux := http.NewServeMux()
 	mux.HandleFunc(getByVersionIdEndPoint, getByVersionIdHandler(transformations))
-	return kithttptest.NewServer(mux)
+	return mux
 }
 
 func getByVersionIdHandler(transformations map[string]string) func(http.ResponseWriter, *http.Request) {

testhelper/httptest/httptest.go

@@ -10,7 +10,7 @@ import (
 // NewServer starts a new httptest server that listens on all interfaces, contrary to the standard net/httptest.Server that listens only on localhost.
 // This is useful when you want to access the test http server from within a docker container.
 func NewServer(handler http.Handler) *Server {
-	ts := newUnStartedServer(handler)
+	ts := NewUnStartedServer(handler)
 	ts.start()
 	return ts
 }
@@ -29,7 +29,7 @@ func (s *Server) start() {
 	s.URL = fmt.Sprintf("http://%s:%s", "localhost", port)
 }
 
-func newUnStartedServer(handler http.Handler) *Server {
+func NewUnStartedServer(handler http.Handler) *Server {
 	return &Server{&nethttptest.Server{
 		Listener: newListener(),
 		Config:   &http.Server{Handler: handler},

testhelper/httptest/httptest_test.go

@@ -43,3 +43,37 @@ func TestServer(t *testing.T) {
 	require.Equal(t, http.StatusOK, statusCode)
 	require.Equal(t, "Hello, world!", string(body))
 }
+
+func TestUnStartedServer(t *testing.T) {
+	// create a server which is not started
+	httpUnStartedServer := kithttptest.NewUnStartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte("Hello, world!"))
+	}))
+
+	var (
+		body       []byte
+		statusCode int
+	)
+	require.Never(t, func() bool {
+		resp, err := http.Get("http://" + httpUnStartedServer.Listener.Addr().String())
+		defer func() { httputil.CloseResponse(resp) }()
+		return err == nil
+	}, 5*time.Second, 10*time.Millisecond, "connected to an un-started server")
+
+	// start the server now
+	httpUnStartedServer.Start()
+	defer httpUnStartedServer.Close()
+
+	require.Eventually(t, func() bool {
+		resp, err := http.Get(httpUnStartedServer.URL)
+		defer func() { httputil.CloseResponse(resp) }()
+		if err == nil {
+			statusCode = resp.StatusCode
+			body, err = io.ReadAll(resp.Body)
+		}
+		return err == nil
+	}, 2*time.Second, 100*time.Millisecond, "failed to connect to server")
+
+	require.Equal(t, http.StatusOK, statusCode)
+	require.Equal(t, "Hello, world!", string(body))
+}