add test with failpoint

Signed-off-by: lhy1024 <[email protected]>

pkg/utils/apiutil/serverapi/middleware.go

@@ -19,6 +19,7 @@ import (
 	"net/url"
 	"strings"
 
+	"github.com/pingcap/failpoint"
 	"github.com/pingcap/log"
 	"github.com/tikv/pd/pkg/errs"
 	"github.com/tikv/pd/pkg/slice"
@@ -171,7 +172,11 @@ func (h *redirector) ServeHTTP(w http.ResponseWriter, r *http.Request, next http
 			return
 		}
 		clientUrls = append(clientUrls, targetAddr)
-		w.Header().Set(apiutil.ForwardToMicroServiceHeader, "true")
+		failpoint.Inject("checkHeader", func() {
+			// add a header to the response, this is not a failure injection
+			// it is used for testing, to check whether the request is forwarded to the micro service
+			w.Header().Set(apiutil.ForwardToMicroServiceHeader, "true")
+		})
 	} else {
 		leader := h.s.GetMember().GetLeader()
 		if leader == nil {

tests/integrations/mcs/scheduling/api_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pingcap/failpoint"
 	"github.com/stretchr/testify/suite"
 	_ "github.com/tikv/pd/pkg/mcs/scheduling/server/apis/v1"
 	"github.com/tikv/pd/pkg/utils/apiutil"
@@ -116,6 +117,11 @@ func (suite *apiTestSuite) TestAPIForward() {
 	defer tc.Destroy()
 	tc.WaitForPrimaryServing(re)
 
+	failpoint.Enable("github.com/tikv/pd/pkg/utils/apiutil/serverapi/checkHeader", "return(true)")
+	defer func() {
+		failpoint.Disable("github.com/tikv/pd/pkg/utils/apiutil/serverapi/checkHeader")
+	}()
+
 	urlPrefix := fmt.Sprintf("%s/pd/api/v1", suite.backendEndpoints)
 	var slice []string
 	var resp map[string]interface{}