diff --git a/server/storage/wal/util_test.go b/server/storage/wal/util_test.go
new file mode 100644
index 000000000000..27407218b85b
--- /dev/null
+++ b/server/storage/wal/util_test.go
@@ -0,0 +1,72 @@
+// Copyright 2026 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 wal
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestIsValidSeq(t *testing.T) {
+	tests := []struct {
+		name  string
+		names []string
+		want  bool
+	}{
+		{
+			name:  "empty slice",
+			names: nil,
+			want:  true,
+		},
+		{
+			name:  "single file",
+			names: []string{walName(0, 0)},
+			want:  true,
+		},
+		{
+			name:  "sequential from zero",
+			names: []string{walName(0, 0), walName(1, 0), walName(2, 0)},
+			want:  true,
+		},
+		{
+			name:  "sequential non-zero start",
+			names: []string{walName(5, 0), walName(6, 0), walName(7, 0)},
+			want:  true,
+		},
+		{
+			name:  "gap in sequence",
+			names: []string{walName(0, 0), walName(1, 0), walName(3, 0)},
+			want:  false,
+		},
+		{
+			name:  "duplicate sequence number",
+			names: []string{walName(0, 0), walName(1, 0), walName(1, 0)},
+			want:  false,
+		},
+		{
+			name:  "two files sequential",
+			names: []string{walName(0, 0), walName(1, 0)},
+			want:  true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := isValidSeq(zaptest.NewLogger(t), tt.names)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}