Improve test documentation based on code review feedback

Co-authored-by: nomeguy <85475922+nomeguy@users.noreply.github.com>

util/process.go

@@ -15,6 +15,7 @@
 package util
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -36,13 +37,17 @@ func getPidByPort(port int) (int, error) {
 
 	output, err := cmd.Output()
 	if err != nil {
+		// If the command is not found (e.g., lsof not installed in Docker),
+		// treat it as no process found on the port
+		if errors.Is(err, exec.ErrNotFound) {
+			return 0, nil
+		}
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			if exitErr.ExitCode() == 1 {
 				return 0, nil
 			}
-		} else {
-			return 0, err
 		}
+		return 0, err
 	}
 
 	lines := strings.Split(string(output), "\n")

util/process_test.go

@@ -0,0 +1,52 @@
+// Copyright 2025 The Casdoor Authors. All Rights Reserved.
+//
+// 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 util
+
+import (
+	"testing"
+)
+
+func TestStopOldInstance(t *testing.T) {
+	// Test that StopOldInstance doesn't panic when lsof is not available
+	// This simulates the Docker environment where lsof is not installed
+	// The function should handle this gracefully and not return an error
+	
+	// Use a high port number (59999) that's unlikely to be in use by other services
+	// This avoids conflicts with commonly used ports (e.g., 8000, 8080, 3000)
+	port := 59999
+	
+	err := StopOldInstance(port)
+	if err != nil {
+		t.Errorf("StopOldInstance should not return error when lsof is not available or port is not in use, got: %v", err)
+	}
+}
+
+func TestGetPidByPort(t *testing.T) {
+	// Test that getPidByPort handles missing lsof gracefully
+	// Use a high port number (59998) that's unlikely to be in use by other services
+	port := 59998
+	
+	pid, err := getPidByPort(port)
+	if err != nil {
+		t.Errorf("getPidByPort should not return error when lsof is not available or port is not in use, got: %v", err)
+	}
+	
+	// When lsof is not available or port is not in use, pid should be 0
+	// Note: If lsof is available and a process is found on this port, pid may be non-zero
+	// This is acceptable as the test's primary goal is to ensure no errors occur
+	if pid != 0 {
+		t.Logf("getPidByPort returned pid %d (a process may be using port %d, or lsof found something)", pid, port)
+	}
+}