Improve code coverage (#236)

Signed-off-by: yhmo <yihua.mo@zilliz.com>

src/main/java/io/milvus/Response/SearchResultsWrapper.java

@@ -114,9 +114,9 @@ public class SearchResultsWrapper {
         @Override
         public String toString() {
             if (strID.isEmpty()) {
-                return "(ID: " + longID + " Score: " + score + ")";
+                return "(ID: " + getLongID() + " Score: " + getScore() + ")";
             } else {
-                return "(ID: '" + strID + "' Score: " + score + ")";
+                return "(ID: '" + getStrID() + "' Score: " + getScore() + ")";
             }
         }
     }

src/test/java/io/milvus/client/MilvusServiceClientTest.java

@@ -2219,6 +2219,7 @@ class MilvusServiceClientTest {
         assertNull(intWrapper.getFieldData("invalid"));
 
         List<SearchResultsWrapper.IDScore> idScores = intWrapper.getIDScore(1);
+        assertFalse(idScores.toString().isEmpty());
         assertEquals(idScores.size(), topK);
         assertThrows(ParamException.class, () -> intWrapper.getIDScore((int) numQueries));
 
@@ -2238,6 +2239,7 @@ class MilvusServiceClientTest {
 
         SearchResultsWrapper strWrapper = new SearchResultsWrapper(results);
         idScores = strWrapper.getIDScore(0);
+        assertFalse(idScores.toString().isEmpty());
         assertEquals(idScores.size(), topK);
 
         idScores.forEach((score)->assertFalse(score.toString().isEmpty()));