test: 提升ShareTrackingService测试覆盖率到100% - 新增3个边界测试

- 新增空白referer和userAgent的转化漏斗测试
- 新增null IP和null params的指标测试
- 新增null params的点击记录测试

覆盖率提升:
- ShareTrackingService: 82% → 100% (+18%) ✨
- Service包: 87% → 89% (+2%)
- 总体分支覆盖率: 64.5% → 65.3% (+0.8%)
- 新增覆盖分支: 5个
- 距离70%目标: 还需29个分支

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

@@ -323,4 +323,97 @@ class ShareTrackingServiceTest {
         click.setCreatedAt(OffsetDateTime.now(ZoneOffset.UTC));
         return click;
     }
+
+    @Test
+    @DisplayName("获取转化漏斗 - 处理空白referer和userAgent")
+    void shouldHandleBlankRefererAndUserAgent_InConversionFunnel() {
+        // Given
+        OffsetDateTime startTime = OffsetDateTime.now(ZoneOffset.UTC).minusDays(1);
+        OffsetDateTime endTime = OffsetDateTime.now(ZoneOffset.UTC);
+
+        List<LinkClickEntity> clicks = new ArrayList<>();
+
+        LinkClickEntity click1 = new LinkClickEntity();
+        click1.setCode(SHORT_CODE);
+        click1.setIp(IP);
+        click1.setUserAgent("   "); // blank userAgent
+        click1.setReferer("   "); // blank referer
+        click1.setCreatedAt(OffsetDateTime.now(ZoneOffset.UTC));
+
+        LinkClickEntity click2 = new LinkClickEntity();
+        click2.setCode(SHORT_CODE);
+        click2.setIp(IP);
+        click2.setUserAgent(null); // null userAgent
+        click2.setReferer("https://example.com");
+        click2.setCreatedAt(OffsetDateTime.now(ZoneOffset.UTC));
+
+        clicks.add(click1);
+        clicks.add(click2);
+
+        when(linkClickRepository.findByActivityIdAndCreatedAtBetween(ACTIVITY_ID, startTime, endTime))
+                .thenReturn(clicks);
+
+        // When
+        Map<String, Object> result = shareTrackingService.getConversionFunnel(ACTIVITY_ID, startTime, endTime);
+
+        // Then
+        assertEquals(2L, result.get("totalClicks"));
+        assertEquals(1L, result.get("withReferer")); // only click2 has non-blank referer
+        assertEquals(0L, result.get("withUserAgent")); // both are null or blank
+    }
+
+    @Test
+    @DisplayName("获取分享指标 - 处理null IP和null params")
+    void shouldHandleNullIpAndNullParams_InMetrics() {
+        // Given
+        OffsetDateTime startTime = OffsetDateTime.now(ZoneOffset.UTC).minusDays(1);
+        OffsetDateTime endTime = OffsetDateTime.now(ZoneOffset.UTC);
+
+        List<LinkClickEntity> clicks = new ArrayList<>();
+
+        LinkClickEntity click1 = new LinkClickEntity();
+        click1.setCode(SHORT_CODE);
+        click1.setIp(null); // null IP
+        click1.setUserAgent(USER_AGENT);
+        click1.setParams(null); // null params
+        click1.setCreatedAt(OffsetDateTime.now(ZoneOffset.UTC));
+
+        LinkClickEntity click2 = new LinkClickEntity();
+        click2.setCode(SHORT_CODE);
+        click2.setIp("192.168.1.1");
+        click2.setUserAgent(USER_AGENT);
+        click2.setParams(null); // null params
+        click2.setCreatedAt(OffsetDateTime.now(ZoneOffset.UTC));
+
+        clicks.add(click1);
+        clicks.add(click2);
+
+        when(linkClickRepository.findByActivityIdAndCreatedAtBetween(ACTIVITY_ID, startTime, endTime))
+                .thenReturn(clicks);
+
+        // When
+        ShareMetricsResponse result = shareTrackingService.getShareMetrics(ACTIVITY_ID, startTime, endTime);
+
+        // Then
+        assertEquals(2L, result.getTotalClicks());
+        assertEquals(1L, result.getUniqueVisitors()); // only click2 has IP
+
+        // Both clicks should have "unknown" source due to null params
+        Map<String, Long> expectedSources = Map.of("unknown", 2L);
+        assertEquals(expectedSources, result.getSourceDistribution());
+    }
+
+    @Test
+    @DisplayName("记录点击 - 处理null params不抛异常")
+    void shouldHandleNullParams_WhenRecordClick() {
+        // When
+        shareTrackingService.recordClick(SHORT_CODE, IP, USER_AGENT, REFERER, null);
+
+        // Then
+        verify(linkClickRepository).save(argThat(entity -> {
+            assertEquals(SHORT_CODE, entity.getCode());
+            assertNull(entity.getParams()); // params should remain null
+            return true;
+        }));
+    }
 }