plugins: adds new no-op plugin that may be used as a test-double

Plugin can be configured to record all inputs and to respond with
arbitrary stdout or error message.  Will support upcoming integration
testing.

plugins/test/noop/debug/debug.go

@@ -0,0 +1,62 @@
+// Copyright 2016 CNI 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.
+
+// debug supports tests that use the noop plugin
+package debug
+
+import (
+	"encoding/json"
+	"io/ioutil"
+
+	"github.com/containernetworking/cni/pkg/skel"
+)
+
+// Debug is used to control and record the behavior of the noop plugin
+type Debug struct {
+	ReportResult string
+	ReportError  string
+	Command      string
+	CmdArgs      skel.CmdArgs
+}
+
+// ReadDebug will return a debug file recorded by the noop plugin
+func ReadDebug(debugFilePath string) (*Debug, error) {
+	debugBytes, err := ioutil.ReadFile(debugFilePath)
+	if err != nil {
+		return nil, err
+	}
+
+	var debug Debug
+	err = json.Unmarshal(debugBytes, &debug)
+	if err != nil {
+		return nil, err
+	}
+
+	return &debug, nil
+}
+
+// WriteDebug will create a debug file to control the noop plugin
+func (debug *Debug) WriteDebug(debugFilePath string) error {
+	debugBytes, err := json.Marshal(debug)
+	if err != nil {
+		return err
+	}
+
+	err = ioutil.WriteFile(debugFilePath, debugBytes, 0600)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}