Add a unit test for range limit

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

Author: Nont

server/etcdserver/txn/range_test.go

@@ -0,0 +1,112 @@
+// Copyright 2025 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package txn
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
+)
+
+func TestRangeLimit(t *testing.T) {
+	tcs := []struct {
+		name    string
+		request *pb.RangeRequest
+		limit   int64
+	}{
+		{
+			name: "Request sort order is not NONE",
+			request: &pb.RangeRequest{
+				SortOrder: pb.RangeRequest_ASCEND,
+				Limit:     1,
+			},
+			limit: 0,
+		},
+		{
+			name: "Request min mod revision is not 0",
+			request: &pb.RangeRequest{
+				SortOrder:      pb.RangeRequest_NONE,
+				MinModRevision: 1,
+				Limit:          1,
+			},
+			limit: 0,
+		},
+		{
+			name: "Request max mod revision is not 0",
+			request: &pb.RangeRequest{
+				SortOrder:      pb.RangeRequest_NONE,
+				MinModRevision: 0,
+				MaxModRevision: 1,
+				Limit:          1,
+			},
+			limit: 0,
+		},
+		{
+			name: "Request min create revision is not 0",
+			request: &pb.RangeRequest{
+				SortOrder:         pb.RangeRequest_NONE,
+				MinModRevision:    0,
+				MaxModRevision:    0,
+				MinCreateRevision: 1,
+				Limit:             1,
+			},
+			limit: 0,
+		},
+		{
+			name: "Request max create revision is not 0",
+			request: &pb.RangeRequest{
+				SortOrder:         pb.RangeRequest_NONE,
+				MinModRevision:    0,
+				MaxModRevision:    0,
+				MinCreateRevision: 0,
+				MaxCreateRevision: 1,
+				Limit:             1,
+			},
+			limit: 0,
+		},
+		{
+			name: "No extra fetch when request limit is 0",
+			request: &pb.RangeRequest{
+				SortOrder:         pb.RangeRequest_NONE,
+				MinModRevision:    0,
+				MaxModRevision:    0,
+				MinCreateRevision: 0,
+				MaxCreateRevision: 0,
+				Limit:             0,
+			},
+			limit: 0,
+		},
+		{
+			name: "Add one extra fetch when request limit is not 0",
+			request: &pb.RangeRequest{
+				SortOrder:         pb.RangeRequest_NONE,
+				MinModRevision:    0,
+				MaxModRevision:    0,
+				MinCreateRevision: 0,
+				MaxCreateRevision: 0,
+				Limit:             1,
+			},
+			limit: 2,
+		},
+	}
+
+	for _, tt := range tcs {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.limit, rangeLimit(tt.request))
+		})
+	}
+}