How to do Junit Test with Google Cloud Pub/Sub - google-cloud-pubsub

Question

I'm using push pub/sub of Google Cloud Pub/Sub in my system,and I want to build my CI test code but I don't know how to do it.For example,some codes are like this:
final Pubsub pubsub = PubsubUtils.getClient();
final PubsubMessage pubsubMessage = new PubsubMessage();
pubsubMessage.encodeData(message.getBytes(StandardCharsets.UTF_8));
Map<String, String> attrs = new HashMap<String, String>();
attrs.put("key", "value");
pubsubMessage.setAttributes(attrs);
final List<PubsubMessage> messages = ImmutableList.of(pubsubMessage);
final PublishRequest publishRequest = new PublishRequest().setMessages(messages);
final PublishResponse publishResponse = pubsub.projects().topics().publish(topic, publishRequest).execute();
final List<String> messageIds = publishResponse.getMessageIds();
and this:
final ServletInputStream reader = request.getInputStream();
try {
// Parse the JSON message to the POJO model class.
final JsonParser parser = JacksonFactory.getDefaultInstance().createJsonParser(reader);
parser.skipToKey("message");
final PubsubMessage message = parser.parseAndClose(PubsubMessage.class);
Map<String, String> attrs = message.getAttributes();
String value = attrs.get("key");
// Base64-decode the data and work with it.
final String data = new String(message.decodeData(), StandardCharsets.UTF_8);
if (data != null || StringUtils.isNotEmpty(data)) {
Logger.getLogger("logger").info(data);
}
// Work with your message
// Respond with a 20X to acknowledge receipt of the message.
response.setStatus(HttpServletResponse.SC_OK);
} finally {
reader.close();
}
How to write a normally Junit test case for the two parts of code? and also,I'm using PowerMockito to mock the objects.
Hope someone can help me.

Answer 1

For unit testing the first example, you can mock the Pub/Sub client object with desired return values for API calls like:
import com.google.api.services.pubsub.Pubsub;
import com.google.api.services.pubsub.Pubsub.Projects;
import com.google.api.services.pubsub.Pubsub.Projects.Topics;
import com.google.api.services.pubsub.Pubsub.Projects.Topics.Create;
import com.google.api.services.pubsub.Pubsub.Projects.Topics.Publish;
// ...
#Mock private Pubsub mockPubsub;
#Mock private Projects mockProjects;
#Mock private Topics mockTopics;
#Mock private Create mockCreate;
#Mock private Publish mockPublish;
// ...
String topicName = "projects/myproject/topics/mytopic";
String messageId = "messageId";
List<String> messageIds = ImmutableList.of(messageId);
PublishResponse publishResponse = new PublishResponse()
.setMessageIds(messageIds);
when(mockPubsub.projects()).thenReturn(mockProjects);
when(mockProjects.topics()).thenReturn(mockTopics);
when(mockTopics.publish(eq(topicName), isA(PublishRequest.class)))
.thenReturn(mockPublish);
when(mockPublish.execute()).thenReturn(publishResponse);
For the second example, you can mock the HttpServletRequest and HttpServletResponse then call the servlet with these mock objects.