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.
#include "google/cloud/pubsub/mocks/mock_publisher_connection.h"
#include "google/cloud/pubsub/publisher.h"
#include <gmock/gmock.h>
The example uses a number of aliases to save typing and improve readability:
using ::google::cloud::pubsub_mocks::MockPublisherConnection;
namespace pubsub = ::google::cloud::pubsub;
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);
And then make calls on the client as usual:
auto id =
publisher.Publish(pubsub::MessageBuilder{}.SetData("test-data-0").Build())
.get();
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 "google/cloud/pubsub/mocks/mock_publisher_connection.h"
#include "google/cloud/pubsub/publisher.h"
#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