Google Cloud Pub/Sub C++ Client  1.31.1
A C++ Client Library for Google Cloud Pub/Sub
Testing your Cloud Pub/Sub publisher application with googlemock

This document describes how to test your own Cloud Pub/Sub application using the Cloud Pub/Sub C++ client library, Google Test and the and Google Test Mocking Framework.

Mocking a Successful Publisher::Publish() call

First include the headers for the Cloud Pub/Sub Publisher Client, the mocking class, and the Google Mock framework.

The example uses a number of aliases to save typing and improve readability:

using ::google::cloud::pubsub_mocks::MockPublisherConnection;
namespace pubsub = ::google::cloud::pubsub;
Contains all the Cloud Pubsub C++ client types and functions.
Definition: ack_handler.cc:20

Create a mocking object for google::cloud::pubsub::PublisherConnection:

auto mock = std::make_shared<MockPublisherConnection>();

It is customary to first setup the expectations for your mock, and then write the rest of the code:

EXPECT_CALL(*mock, Publish)
.WillOnce([&](pubsub::PublisherConnection::PublishParams const& p) {
EXPECT_EQ("test-data-0", p.message.data());
return google::cloud::make_ready_future(
google::cloud::StatusOr<std::string>("test-id-0"));
});

With the expectations in place, create a google::cloud::pubsub::Publisher object:

pubsub::Publisher publisher(mock);
Publish messages to the Cloud Pub/Sub service.
Definition: publisher.h:98

And then make calls on the client as usual:

auto id =
publisher.Publish(pubsub::MessageBuilder{}.SetData("test-data-0").Build())
.get();
Constructs Message objects.
Definition: message.h:144
MessageBuilder & SetData(std::string data) &
Sets the message payload to data.
Definition: message.h:152

And then verify the results meet your expectations:

EXPECT_TRUE(id.ok());
EXPECT_EQ("test-id-0", *id);

Full Listing

Finally we present the full code for this example:

#include <gmock/gmock.h>
namespace {
using ::google::cloud::pubsub_mocks::MockPublisherConnection;
namespace pubsub = ::google::cloud::pubsub;
TEST(MockPublishExample, PublishSimple) {
auto mock = std::make_shared<MockPublisherConnection>();
EXPECT_CALL(*mock, Publish)
.WillOnce([&](pubsub::PublisherConnection::PublishParams const& p) {
EXPECT_EQ("test-data-0", p.message.data());
return google::cloud::make_ready_future(
google::cloud::StatusOr<std::string>("test-id-0"));
});
pubsub::Publisher publisher(mock);
auto id =
publisher.Publish(pubsub::MessageBuilder{}.SetData("test-data-0").Build())
.get();
EXPECT_TRUE(id.ok());
EXPECT_EQ("test-id-0", *id);
}
} // namespace