Limit the response size of ExecSync

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

pkg/cri/server/container_execsync_test.go

@@ -0,0 +1,49 @@
+/*
+   Copyright The containerd 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 server
+
+import (
+	"bytes"
+	"testing"
+
+	cioutil "github.com/containerd/containerd/pkg/ioutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCWWrite(t *testing.T) {
+	var buf bytes.Buffer
+	cw := &cappedWriter{w: cioutil.NewNopWriteCloser(&buf), remain: 10}
+
+	n, err := cw.Write([]byte("hello"))
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	n, err = cw.Write([]byte("helloworld"))
+	assert.Equal(t, []byte("hellohello"), buf.Bytes(), "partial write")
+	assert.Equal(t, 5, n)
+	assert.ErrorIs(t, err, errNoRemain)
+
+	_, err = cw.Write([]byte("world"))
+	assert.ErrorIs(t, err, errNoRemain)
+}
+
+func TestCWClose(t *testing.T) {
+	var buf bytes.Buffer
+	cw := &cappedWriter{w: cioutil.NewNopWriteCloser(&buf), remain: 5}
+	err := cw.Close()
+	assert.NoError(t, err)
+}