Enhance security and reliability across SFTP workflows

src/test/java/com/sftp/manager/service/LocalFileServiceTest.java

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+package com.sftp.manager.service;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.File;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+public class LocalFileServiceTest {
+
+    private final LocalFileService localFileService = new LocalFileService();
+
+    @TempDir
+    Path tempDir;
+
+    @Test
+    public void createDirectory_shouldRejectParentTraversalPath() {
+        String badPath = tempDir.resolve("../escape-dir").toString();
+
+        Exception ex = Assertions.assertThrows(Exception.class,
+                () -> localFileService.createDirectory(badPath));
+
+        Assertions.assertTrue(ex.getMessage().contains("上级目录引用"));
+    }
+
+    @Test
+    public void deleteFile_shouldRejectRootPath() {
+        File[] roots = File.listRoots();
+        Assertions.assertNotNull(roots);
+        Assertions.assertTrue(roots.length > 0);
+
+        String rootPath = roots[0].getPath();
+
+        Exception ex = Assertions.assertThrows(Exception.class,
+                () -> localFileService.deleteFile(rootPath));
+
+        Assertions.assertTrue(ex.getMessage().contains("根目录禁止删除"));
+    }
+
+    @Test
+    public void renameFile_shouldRejectCrossDirectoryRename() throws Exception {
+        Path source = tempDir.resolve("source.txt");
+        Files.write(source, "data".getBytes(StandardCharsets.UTF_8));
+
+        Path subDir = tempDir.resolve("sub");
+        Files.createDirectories(subDir);
+        Path target = subDir.resolve("target.txt");
+
+        Exception ex = Assertions.assertThrows(Exception.class,
+                () -> localFileService.renameFile(source.toString(), target.toString()));
+
+        Assertions.assertTrue(ex.getMessage().contains("仅支持同目录重命名"));
+    }
+
+    @Test
+    public void renameFile_shouldAllowRenameInSameDirectory() throws Exception {
+        Path source = tempDir.resolve("old-name.txt");
+        Files.write(source, "data".getBytes(StandardCharsets.UTF_8));
+        Path target = tempDir.resolve("new-name.txt");
+
+        boolean result = localFileService.renameFile(source.toString(), target.toString());
+
+        Assertions.assertTrue(result);
+        Assertions.assertFalse(Files.exists(source));
+        Assertions.assertTrue(Files.exists(target));
+    }
+
+    @Test
+    public void fileExists_shouldReturnFalseWhenPathContainsTraversal() {
+        boolean exists = localFileService.fileExists("../sensitive-path");
+
+        Assertions.assertFalse(exists);
+    }
+}