Add Prepend() for prepending mathcher

grpcstub.go

@@ -134,6 +134,7 @@ type Server struct {
 	healthCheck       bool
 	disableReflection bool
 	status            serverStatus
+	prependOnce       bool
 	t                 TB
 	mu                sync.RWMutex
 }
@@ -326,7 +327,7 @@ func (s *Server) Match(fn func(req *Request) bool) *matcher {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	s.matchers = append(s.matchers, m)
+	s.addMatcher(m)
 	return m
 }
 
@@ -347,7 +348,7 @@ func (s *Server) Service(service string) *matcher {
 		matchFuncs: []matchFunc{fn},
 		t:          s.t,
 	}
-	s.matchers = append(s.matchers, m)
+	s.addMatcher(m)
 	return m
 }
 
@@ -379,7 +380,7 @@ func (s *Server) Method(method string) *matcher {
 		matchFuncs: []matchFunc{fn},
 		t:          s.t,
 	}
-	s.matchers = append(s.matchers, m)
+	s.addMatcher(m)
 	return m
 }
 
@@ -517,6 +518,14 @@ func (s *Server) ClearMatchers() {
 	s.matchers = nil
 }
 
+// Prepend prepend matcher.
+func (s *Server) Prepend() *Server {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.prependOnce = true
+	return s
+}
+
 // ClearRequests clear requests.
 func (s *Server) ClearRequests() {
 	s.requests = nil
@@ -530,6 +539,15 @@ func (m *matcher) Requests() []*Request {
 	return m.requests
 }
 
+func (s *Server) addMatcher(m *matcher) {
+	if s.prependOnce {
+		s.matchers = append([]*matcher{m}, s.matchers...)
+		s.prependOnce = false
+		return
+	}
+	s.matchers = append(s.matchers, m)
+}
+
 func (s *Server) registerServer() {
 	for _, fd := range s.fds {
 		for i := 0; i < fd.Services().Len(); i++ {

grpcstub_test.go

@@ -804,3 +804,53 @@ func TestUnmarshalProtoMessage(t *testing.T) {
 		t.Errorf("got %v\nwant %v", got, want)
 	}
 }
+
+func TestPrepend(t *testing.T) {
+	t.Run("Default", func(t *testing.T) {
+		ctx := context.Background()
+		ts := NewServer(t, "testdata/route_guide.proto")
+		t.Cleanup(func() {
+			ts.Close()
+		})
+		ts.Service("routeguide.RouteGuide").Response(map[string]any{"name": "hello"})
+		ts.Service("routeguide.RouteGuide").Response(map[string]any{"name": "world"})
+		ts.Service("routeguide.RouteGuide").Response(map[string]any{"name": "!!!"})
+
+		client := routeguide.NewRouteGuideClient(ts.Conn())
+		res, err := client.GetFeature(ctx, &routeguide.Point{
+			Latitude:  10,
+			Longitude: 13,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		got := res.Name
+		if want := "hello"; got != want {
+			t.Errorf("got %v\nwant %v", got, want)
+		}
+	})
+
+	t.Run("Prepend", func(t *testing.T) {
+		ctx := context.Background()
+		ts := NewServer(t, "testdata/route_guide.proto")
+		t.Cleanup(func() {
+			ts.Close()
+		})
+		ts.Service("routeguide.RouteGuide").Response(map[string]any{"name": "hello"})
+		ts.Prepend().Service("routeguide.RouteGuide").Response(map[string]any{"name": "world"})
+		ts.Service("routeguide.RouteGuide").Response(map[string]any{"name": "!!!"})
+
+		client := routeguide.NewRouteGuideClient(ts.Conn())
+		res, err := client.GetFeature(ctx, &routeguide.Point{
+			Latitude:  10,
+			Longitude: 13,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		got := res.Name
+		if want := "world"; got != want {
+			t.Errorf("got %v\nwant %v", got, want)
+		}
+	})
+}