go-by-test/racer/racer_test.go

package racer

import (
	"net/http"
	"net/http/httptest"
	"testing"
	"time"
)

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()

		fastServer := makeDelayedServer(0 * time.Millisecond)
		defer fastServer.Close()

		slowURL := slowServer.URL
		fastURL := fastServer.URL

		want := 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 {
	return httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			time.Sleep(delay)
			w.WriteHeader(http.StatusOK)
		}))
}