Test success case of using WaitForPort func.

tools/testtool/freeport_test.go

@@ -2,6 +2,10 @@ package testtool
 
 import (
 	"context"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
 	"testing"
 	"time"
 
@@ -15,6 +19,23 @@ func TestGetFreePort(t *testing.T) {
 }
 
 func TestWaitForPort(t *testing.T) {
+	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
+	defer s.Close()
+
+	u, err := url.Parse(s.URL)
+	require.Nil(t, err)
+	_, port, err := net.SplitHostPort(u.Host)
+	require.Nil(t, err)
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	WaitForPort(ctx, port)
+
+	require.NoError(t, ctx.Err())
+}
+
+func TestWaitForPort_timeout(t *testing.T) {
 	p, err := GetFreePort()
 	require.NoError(t, err)