pkg/invoke: refactor plugin exec and backfill unit tests

invoke/fakes/raw_exec.go

@@ -0,0 +1,36 @@
+// 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.
+
+package fakes
+
+type RawExec struct {
+	ExecPluginCall struct {
+		Received struct {
+			PluginPath string
+			StdinData  []byte
+			Environ    []string
+		}
+		Returns struct {
+			ResultBytes []byte
+			Error       error
+		}
+	}
+}
+
+func (e *RawExec) ExecPlugin(pluginPath string, stdinData []byte, environ []string) ([]byte, error) {
+	e.ExecPluginCall.Received.PluginPath = pluginPath
+	e.ExecPluginCall.Received.StdinData = stdinData
+	e.ExecPluginCall.Received.Environ = environ
+	return e.ExecPluginCall.Returns.ResultBytes, e.ExecPluginCall.Returns.Error
+}