fix(fcm): Added toString() in TopicManagementResponse for logging (#469)

* Added toString() in TopicManagementResponse for logging (#343)

* Used MoreObjects.toStringHelper()

* removed .DS_Store & added it to .gitignore

* unit test case for TopicManagementResponse toString() functionality added for logging

* fixed checkStyle issue of line should not greater than 100 char

Author: shambhand

.gitignore

@@ -10,3 +10,4 @@ target/
 release.properties
 integration_cert.json
 integration_apikey.txt
+.DS_Store

src/main/java/com/google/firebase/messaging/TopicManagementResponse.java

@@ -20,6 +20,7 @@
 import static com.google.common.base.Preconditions.checkState;
 
 import com.google.api.client.json.GenericJson;
+import com.google.common.base.MoreObjects;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.firebase.internal.NonNull;
@@ -122,5 +123,13 @@ public int getIndex() {
     public String getReason() {
       return reason;
     }
+
+    @Override
+    public String toString() {
+      return MoreObjects.toStringHelper(this)
+              .add("index", index)
+              .add("reason", reason)
+              .toString();
+    }
   }
 }

src/test/java/com/google/firebase/messaging/InstanceIdClientImplTest.java

@@ -340,6 +340,17 @@ public void testTopicManagementResponseWithEmptyList() {
     new TopicManagementResponse(ImmutableList.<GenericJson>of());
   }
 
+  @Test
+  public void testTopicManagementResponseErrorToString() {
+    GenericJson json = new GenericJson().set("error", "test error");
+    ImmutableList<GenericJson> jsonList = ImmutableList.of(json);
+
+    TopicManagementResponse topicManagementResponse = new TopicManagementResponse(jsonList);
+
+    String expected = "[Error{index=0, reason=unknown-error}]";
+    assertEquals(expected, topicManagementResponse.getErrors().toString());
+  }
+
   private static InstanceIdClientImpl initInstanceIdClient(
       final MockLowLevelHttpResponse mockResponse,
       final HttpResponseInterceptor interceptor) {