Testing your Cloud IAM Credentials application with googlemock

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

Mocking a Successful IAMCredentialsClient::SignJwt() call

First include the headers for the Cloud IAM Credentials Client, the mocking class, and the Google Mock framework:

#include "google/cloud/iam/credentials/v1/iam_credentials_client.h"
#include "google/cloud/iam/credentials/v1/mocks/mock_iam_credentials_connection.h"
#include <gmock/gmock.h>

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

using ::google::cloud::iam_credentials_v1_mocks::MockIAMCredentialsConnection;
namespace iam = ::google::cloud::iam_credentials_v1;

Create a mocking object for google::cloud::iam_credentials_v1::IAMCredentialsConnection:

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

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

  EXPECT_CALL(*mock, SignJwt)
      .WillOnce(
          [&](google::iam::credentials::v1::SignJwtRequest const& request) {
            EXPECT_EQ("projects/-/serviceAccounts/test-account-unique-id",
                      request.name());
            google::iam::credentials::v1::SignJwtResponse response;
            response.set_key_id("test-key-id");
            return google::cloud::StatusOr<
                google::iam::credentials::v1::SignJwtResponse>(response);
          });

With the expectations in place, create a google::cloud::iam_credentials_v1::IAMCredentialsClient object:

  iam::IAMCredentialsClient iam_credentials_client(mock);

And then make calls on the client as usual:

  std::string payload;
  auto response = iam_credentials_client.SignJwt(
      "projects/-/serviceAccounts/test-account-unique-id", {}, payload);

And then verify the results meet your expectations:

  EXPECT_TRUE(response.ok());
  EXPECT_EQ("test-key-id", response->key_id());

Full Listing

Finally we present the full code for this example:

#include "google/cloud/iam/credentials/v1/iam_credentials_client.h"
#include "google/cloud/iam/credentials/v1/mocks/mock_iam_credentials_connection.h"
#include <gmock/gmock.h>

namespace {

using ::google::cloud::iam_credentials_v1_mocks::MockIAMCredentialsConnection;
namespace iam = ::google::cloud::iam_credentials_v1;

TEST(MockSignJwtExample, SignJwt) {
  auto mock = std::make_shared<MockIAMCredentialsConnection>();

  EXPECT_CALL(*mock, SignJwt)
      .WillOnce(
          [&](google::iam::credentials::v1::SignJwtRequest const& request) {
            EXPECT_EQ("projects/-/serviceAccounts/test-account-unique-id",
                      request.name());
            google::iam::credentials::v1::SignJwtResponse response;
            response.set_key_id("test-key-id");
            return google::cloud::StatusOr<
                google::iam::credentials::v1::SignJwtResponse>(response);
          });

  iam::IAMCredentialsClient iam_credentials_client(mock);

  std::string payload;
  auto response = iam_credentials_client.SignJwt(
      "projects/-/serviceAccounts/test-account-unique-id", {}, payload);

  EXPECT_TRUE(response.ok());
  EXPECT_EQ("test-key-id", response->key_id());
}

}  // namespace