test: add unit test for main function

cmd/smbplugin/main.go

@@ -51,6 +51,11 @@ var (
 	removeArchivedVolumePath      = flag.Bool("remove-archived-volume-path", true, "remove archived volume path in DeleteVolume")
 )
 
+// exit is a separate function to handle program termination
+var exit = func(code int) {
+	os.Exit(code)
+}
+
 func main() {
 	flag.Parse()
 	if *ver {
@@ -59,15 +64,15 @@ func main() {
 			klog.Fatalln(err)
 		}
 		fmt.Println(info) // nolint
-		os.Exit(0)
-	}
-	if *nodeID == "" {
-		// nodeid is not needed in controller component
-		klog.Warning("nodeid is empty")
+	} else {
+		if *nodeID == "" {
+			// nodeid is not needed in controller component
+			klog.Warning("nodeid is empty")
+		}
+		exportMetrics()
+		handle()
 	}
-	exportMetrics()
-	handle()
-	os.Exit(0)
+	exit(0)
 }
 
 func handle() {

cmd/smbplugin/main_test.go

@@ -0,0 +1,82 @@
+/*
+Copyright 2024 The Kubernetes 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 main
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestMain(t *testing.T) {
+	// Set the version flag to true
+	os.Args = []string{"cmd", "-ver"}
+
+	// Capture stdout
+	old := os.Stdout
+	_, w, _ := os.Pipe()
+	os.Stdout = w
+
+	// Replace exit function with mock function
+	var exitCode int
+	exit = func(code int) {
+		exitCode = code
+	}
+
+	// Call main function
+	main()
+
+	// Restore stdout
+	w.Close()
+	os.Stdout = old
+	exit = func(code int) {
+		os.Exit(code)
+	}
+
+	if exitCode != 0 {
+		t.Errorf("Expected exit code 0, but got %d", exitCode)
+	}
+}
+
+func TestTrapClosedConnErr(t *testing.T) {
+	tests := []struct {
+		err         error
+		expectedErr error
+	}{
+		{
+			err:         net.ErrClosed,
+			expectedErr: nil,
+		},
+		{
+			err:         nil,
+			expectedErr: nil,
+		},
+		{
+			err:         fmt.Errorf("some error"),
+			expectedErr: fmt.Errorf("some error"),
+		},
+	}
+
+	for _, test := range tests {
+		err := trapClosedConnErr(test.err)
+		if !reflect.DeepEqual(err, test.expectedErr) {
+			t.Errorf("Expected error %v, but got %v", test.expectedErr, err)
+		}
+	}
+}