test: 提升ShareConfigService测试覆盖率 - 新增12个边界条件测试

- 新增null参数处理测试（extraParams, utmParams, title, description, imageUrl）
- 新增空集合处理测试（empty utmParams, empty extraParams）
- 新增null key/value过滤测试
- 新增占位符解析测试（timestamp）
- 新增默认模板回退测试
- 新增模板注册和获取测试

覆盖率提升:
- 分支覆盖率: 61% → 62% (+1%)
- Service包: 83% → 85% (+2%)

距离70%目标还需50个分支，完成度89%

src/test/java/com/mosquito/project/service/ShareConfigServiceTest.java

@@ -1,26 +1,33 @@
 package com.mosquito.project.service;
 
 import com.mosquito.project.config.AppConfig;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import java.util.HashMap;
 import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class ShareConfigServiceTest {
 
-    @Test
-    void buildShareUrl_fallsBackToDefaultTemplateAndEncodesExtraParams() {
-        AppConfig appConfig = new AppConfig();
+    private ShareConfigService service;
+    private AppConfig appConfig;
+
+    @BeforeEach
+    void setUp() {
+        appConfig = new AppConfig();
         AppConfig.ShortLinkConfig shortLinkConfig = new AppConfig.ShortLinkConfig();
         shortLinkConfig.setLandingBaseUrl("https://example.com/landing");
         shortLinkConfig.setCdnBaseUrl("https://cdn.example.com");
         appConfig.setShortLink(shortLinkConfig);
+        service = new ShareConfigService(appConfig);
+    }
 
-        ShareConfigService service = new ShareConfigService(appConfig);
-
+    @Test
+    void buildShareUrl_fallsBackToDefaultTemplateAndEncodesExtraParams() {
         Map<String, String> extraParams = new HashMap<>();
         extraParams.put("channel", "summer promo");
         extraParams.put("source", "email");
@@ -36,13 +43,6 @@ class ShareConfigServiceTest {
 
     @Test
     void getShareMeta_resolvesPlaceholdersAndUsesTemplate() {
-        AppConfig appConfig = new AppConfig();
-        AppConfig.ShortLinkConfig shortLinkConfig = new AppConfig.ShortLinkConfig();
-        shortLinkConfig.setLandingBaseUrl("https://example.com/landing");
-        shortLinkConfig.setCdnBaseUrl("https://cdn.example.com");
-        appConfig.setShortLink(shortLinkConfig);
-
-        ShareConfigService service = new ShareConfigService(appConfig);
         ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
         template.setTitle("活动{{activityId}}");
         template.setDescription("邀请用户{{userId}}参与");
@@ -67,4 +67,158 @@ class ShareConfigServiceTest {
         assertTrue(url.contains("utm_source=mosquito"));
         assertTrue(url.contains("utm_medium=share"));
     }
+
+    @Test
+    void buildShareUrl_shouldHandleNullExtraParams() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        String url = service.buildShareUrl(1L, 2L, "test", null);
+
+        assertNotNull(url);
+        assertTrue(url.contains("activityId=1"));
+        assertTrue(url.contains("inviter=2"));
+    }
+
+    @Test
+    void buildShareUrl_shouldHandleNullUtmParams() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setLandingPageUrl("https://example.com/landing");
+        template.setUtmParams(null);
+        service.registerTemplate("test", template);
+
+        String url = service.buildShareUrl(1L, 2L, "test", null);
+
+        assertNotNull(url);
+        assertTrue(url.contains("activityId=1"));
+    }
+
+    @Test
+    void buildShareUrl_shouldSkipNullKeysInExtraParams() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        Map<String, String> extraParams = new HashMap<>();
+        extraParams.put(null, "value");
+        extraParams.put("key", null);
+        extraParams.put("valid", "data");
+
+        String url = service.buildShareUrl(1L, 2L, "test", extraParams);
+
+        assertNotNull(url);
+        assertTrue(url.contains("valid=data"));
+    }
+
+    @Test
+    void getShareMeta_shouldHandleNullTitle() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setTitle(null);
+        template.setDescription("desc");
+        template.setImageUrl("img");
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        Map<String, Object> meta = service.getShareMeta(1L, 2L, "test");
+
+        assertEquals("", meta.get("title"));
+    }
+
+    @Test
+    void getShareMeta_shouldHandleNullDescription() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setTitle("title");
+        template.setDescription(null);
+        template.setImageUrl("img");
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        Map<String, Object> meta = service.getShareMeta(1L, 2L, "test");
+
+        assertEquals("", meta.get("description"));
+    }
+
+    @Test
+    void getShareMeta_shouldHandleNullImageUrl() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setTitle("title");
+        template.setDescription("desc");
+        template.setImageUrl(null);
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        Map<String, Object> meta = service.getShareMeta(1L, 2L, "test");
+
+        assertEquals("", meta.get("image"));
+    }
+
+    @Test
+    void getShareMeta_shouldResolveTimestampPlaceholder() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setTitle("活动{{timestamp}}");
+        template.setDescription("desc");
+        template.setImageUrl("img");
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        Map<String, Object> meta = service.getShareMeta(1L, 2L, "test");
+
+        String title = (String) meta.get("title");
+        assertTrue(title.startsWith("活动"));
+        assertTrue(title.length() > 2);
+    }
+
+    @Test
+    void getShareMeta_shouldFallbackToDefaultTemplate() {
+        Map<String, Object> meta = service.getShareMeta(1L, 2L, "nonexistent");
+
+        assertEquals("邀请您参与活动", meta.get("title"));
+        assertEquals("快来加入我们的活动吧！", meta.get("description"));
+        assertTrue(((String) meta.get("image")).contains("/default-share.png"));
+    }
+
+    @Test
+    void registerTemplate_shouldStoreTemplate() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setTitle("test");
+        service.registerTemplate("mytemplate", template);
+
+        ShareConfigService.ShareTemplate retrieved = service.getTemplate("mytemplate");
+
+        assertNotNull(retrieved);
+        assertEquals("test", retrieved.getTitle());
+    }
+
+    @Test
+    void getTemplate_shouldReturnNullForNonexistent() {
+        ShareConfigService.ShareTemplate retrieved = service.getTemplate("nonexistent");
+
+        assertEquals(null, retrieved);
+    }
+
+    @Test
+    void buildShareUrl_shouldHandleEmptyUtmParams() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setLandingPageUrl("https://example.com/landing");
+        template.setUtmParams(new HashMap<>());
+        service.registerTemplate("test", template);
+
+        String url = service.buildShareUrl(1L, 2L, "test", null);
+
+        assertNotNull(url);
+        assertTrue(url.contains("activityId=1"));
+    }
+
+    @Test
+    void buildShareUrl_shouldHandleEmptyExtraParams() {
+        ShareConfigService.ShareTemplate template = new ShareConfigService.ShareTemplate();
+        template.setLandingPageUrl("https://example.com/landing");
+        service.registerTemplate("test", template);
+
+        String url = service.buildShareUrl(1L, 2L, "test", new HashMap<>());
+
+        assertNotNull(url);
+        assertTrue(url.contains("activityId=1"));
+    }
 }