添加对JwtUtil的单元测试，确保功能可用

src/test/java/org/cmh/backend/Utils/JwtUtilTest.java

@@ -0,0 +1,47 @@
+package org.cmh.backend.Utils;
+
+import io.jsonwebtoken.Claims;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Date;
+
+public class JwtUtilTest {
+
+    @Test
+    public void testGenerateToken() throws InterruptedException {
+        String username = "testUser";
+        String token = JwtUtil.generateToken(username);
+        Thread.sleep(100);
+
+        // Validate token is not empty
+        Assert.assertNotNull("Token should not be null", token);
+        Assert.assertFalse("Token should not be empty", token.isEmpty());
+
+        // Parse the token to check claims
+        Claims claims = JwtUtil.extractClaims(token);
+//        System.out.println(claims.getIssuedAt().toString());
+
+
+        // Validate claims
+        Assert.assertTrue("Token shoud be valid", JwtUtil.isTokenValid(token, username));
+        Assert.assertEquals("Username in claims should match", username, claims.getSubject());
+        Assert.assertTrue("Token should be issued in the past", new Date().after(claims.getIssuedAt()));
+        Assert.assertTrue("Token expiration should be in the future", new Date().before(claims.getExpiration()));
+    }
+
+    @Test
+    public void testTokenExpiration() {
+        String username = "testUser";
+        String token = JwtUtil.generateToken(username);
+
+        Claims claims = JwtUtil.extractClaims(token);
+
+        long expirationTime = claims.getExpiration().getTime();
+        long currentTime = new Date().getTime();
+
+        // Validate token expires within 10 hours
+        Assert.assertTrue("Token should expire within 10 hours", expirationTime - currentTime <= 1000 * 60 * 60 * 10);
+    }
+}
+