racer: add timeout test

racer/racer.go

@@ -1,29 +1,23 @@
 package racer
 
 import (
-	"fmt"
+	"errors"
 	"net/http"
 	"time"
 )
 
-func Racer(a, b string) string {
+func Racer(a, b string) (string, error) {
 	select {
 	// wait until channel closed
 	case <-ping(a):
-		return a
+		return a, nil
 	case <-ping(b):
-		return b
+		return b, nil
+	case <-time.After(10 * time.Second):
+		return "", errors.New("timeout")
 	}
 }
 
-func measureResponseTime(url string) time.Duration {
-	start := time.Now()
-	http.Get(url)
-	duration := time.Since(start)
-	fmt.Println(duration)
-	return duration
-}
-
 func ping(url string) chan struct{} {
 	ch := make(chan struct{})
 	go func() {
@@ -33,3 +27,11 @@ func ping(url string) chan struct{} {
 	}()
 	return ch
 }
+
+// func measureResponseTime(url string) time.Duration {
+// 	start := time.Now()
+// 	http.Get(url)
+// 	duration := time.Since(start)
+// 	fmt.Println(duration)
+// 	return duration
+// }

racer/racer_test.go

@@ -8,6 +8,7 @@ import (
 )
 
 func TestRacer(t *testing.T) {
+	t.Run("compares speeds of servers, returning the url of the fasted one", func(t *testing.T) {
 		slowServer := makeDelayedServer(20 * time.Millisecond)
 		defer slowServer.Close()
 
@@ -18,11 +19,25 @@ func TestRacer(t *testing.T) {
 		fastURL := fastServer.URL
 
 		want := fastURL
-	got := Racer(slowURL, fastURL)
+		got, _ := Racer(slowURL, fastURL)
 
 		if got != want {
 			t.Errorf("got %q, want %q", got, want)
 		}
+	})
+
+	t.Run("returns an error if a server doesn't respond within 10s", func(t *testing.T) {
+		serverA := makeDelayedServer(11 * time.Second)
+		defer serverA.Close()
+
+		serverB := makeDelayedServer(11 * time.Second)
+		defer serverB.Close()
+
+		_, err := Racer(serverA.URL, serverB.URL)
+		if err == nil {
+			t.Error("expected an error but didn't got one")
+		}
+	})
 }
 
 func makeDelayedServer(delay time.Duration) *httptest.Server {