Mocking ros::Time::now in rostest/gtest

Question

I am running the tests for my ROS C++ node using rostest/gtest.

Currently I have a problem where I have a class method that I need/want to test that out of date data based on the value of ros::Time::now();. Since the data that I am using for this test has a predefined date I need/want to mock the value returned by ros::Time::now();. I have seen that I should be able to achieve this by setting /use_sim_time to true for example in the launch file and then publishing in the /clock topic.

However when doing this the test execution does not return and simply times out, even when nothing is really being tested. The test execution runs fine without this.

I am executing my tests with catkin run_tests.

In this scenario:

• Setting <param name="/use_sim_time" value="true"/> in the launch file.
• On the main of my unittests node, I am publishing a message to /clock with msg.clock = ros::Time(1678456559, 0);.

Then I get the following executing the test.

[ WARN] [1709049828.959657287]: Main ros::Time::now() = 0.000000
[ WARN] [1709049828.960573171, 1678456559.000000000]: Test class Constructor ros::Time::now() = 1678456559.000000
[ WARN] [1709049828.960620129, 1678456559.000000000]: Test class SetUp ros::Time::now() = 1678456559.000000

It's weird that the first log has ros::Time::now() has a value of 0.0 even though it is after the message has been published.

    ros::NodeHandle nh;

    rosgraph_msgs::Clock msg;
    msg.clock = ros::Time(1678456559, 0);

    ros::Publisher clock_pub = nh.advertise<rosgraph_msgs::Clock>("/clock", 1);

    clock_pub.publish(msg);

    ros::spinOnce();

    ROS_WARN("Main ros::Time::now() = %f", ros::Time::now().toSec());

Then it's also weird that there are two timestamps in the log messages from then on. The values are correct however, but the code hangs when I create the unique_ptr to my class.

test_pr = std::make_unique<MyClassTest>();

What am I doing wrong/missing?

Thank you all in advance

Edit: After a bit more debugging it seems that what I did initially was correct. However I found that one the classes that I'm testing, initializes an object that has a small sleep in the constructor. Since with use_sim_time the time is "stopped" this sleep would never complete and it would time out.

I added a new thread that published to the clock topic to overcome this and it seems to work. Now I can set the initial time and make sure it doesn't stop.

Answer 1

I was missing:

void clock(ros::NodeHandle& nh, const uint32_t start_time) {
rosgraph_msgs::Clock msg;
msg.clock = ros::Time(start_time, 0);

ros::Publisher clock_pub_ = nh.advertise<rosgraph_msgs::Clock>("/clock", 1);

while (ros::ok()) {
    clock_pub_.publish(msg);
    ros::WallDuration(0.2).sleep();
    msg.clock = ros::Time(ros::Time::now().toSec() + 1);
}

And then in main

    // Start clock thread
std::thread clock_thread([&]() { clock(nh, 1678456559); });

Answer 2

First, I think there's an answer here that addresses your issue:

As noted in the rospy Time overview, one workaround is to loop the assignment until it returns a non-zero value:

prevTime = 0
while not prevTime:
    prevTime = rospy.Time.now()

but you can also mock easier if you create and code against and interface; interfaces let you swap implementations easily. Something like:

class IGetTime
{
  public:
    virtual ros::Time getTime() = 0;
}
class GetTimeRos : public IGetTime
{
  public:
    ros::Time getCurrentTime() final { return ros::Time::now(); }
}
class GetTimeMock : public IGetTime
{
  public:
    ros::Time getCurrentTime() final { ros::Time(1678456559, 0); }
}

then in your code you can do something like:

IGetTime time_getter = GetTimeRos();
my_timed_method.doStuff(time_getter.getCurrentTime());

and in your test you can:

IGetTime mock_time_getter = GetTimeMock();
my_timed_method.doStuff(mock_time_getter.getCurrentTime());