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Hi helpful ROS answer-ers,

Due to a recent epiphany I have hopped aboard the TDD train, so to give you some context I am pretty new to working with unit testing frameworks, in particular gtest. I recently began working on a simple package to handle some i/o using a phidgets board I had sitting around, and decided to start there with ROS TDD, however I have been having some issues getting off the ground.

So I have a package setup in the following way: scatter_phidgets /src/scatter_phidgets.cpp /include/scatter_phidgets/scatter_phidgets.h /tests/utest.cpp

my Cmakelist looks like this:

cmake_minimum_required(VERSION 2.8.3)
project(scatter_phidgets)

add_definitions(-std=c++11)

find_package(catkin REQUIRED COMPONENTS
  roscpp
  std_msgs
  phidgets_api
  message_generation
)

add_message_files(
  FILES
  DigitalInput.msg
)

generate_messages(
  DEPENDENCIES
  std_msgs
)

catkin_package(
  INCLUDE_DIRS include
  CATKIN_DEPENDS roscpp std_msgs phidgets_api message_runtime
  DEPENDS system_lib
)

include_directories(include ${catkin_INCLUDE_DIRS})
add_executable(phidgets src/scatter_phidgets.cpp)
target_link_libraries(phidgets ${catkin_LIBRARIES})

if (CATKIN_ENABLE_TESTING)
  catkin_add_gtest(utest test/utest.cpp)
  target_link_libraries(utest ${catkin_LIBRARIES})
endif()

In the header file I have a struct defined for digital inputs, digital outputs, analog outputs, along with the declaration of a single function that I wish to perform the unit test on, and looks like this:

#ifndef SCATTER_PHIDGETS_INCLUDE_SCATTER_PHIDGETS_SCATTER_PHIDGETS_H_
#define SCATTER_PHIDGETS_INCLUDE_SCATTER_PHIDGETS_SCATTER_PHIDGETS_H_

#include <queue>
#include <ros/ros.h>


struct digital_input{
    int channel;
    ros::Publisher publisher;
    ros::Subscriber subscriber;
    bool latching = false;
    int low_state = 0;
    int latch_timeout = 0;
    bool leading_edge = false;
    int x_out_of = 0;
    int y_sample_size = 0;
    // ---------------------------
    std::queue<int> values;
    int sum = 0;
    int publish_value = 0;
    bool latched = false;
    bool hold_pending = false;
    ros::Time time_latched;
    ros::Time hold_start;
    uint32_t held_time;
};

struct analog_input{
    int channel;
    ros::Publisher publisher;
    // ---------------------------
    int value = 0;
};

struct digital_output{
    int channel;
    ros::Publisher publisher;
    ros::Subscriber subscriber;
    int default_state = 0;
    // ---------------------------
    int value_actual = 0;
    int value_commanded = 0;
};

void updateQueue(digital_input input, int raw_state);


#endif /* SCATTER_PHIDGETS_INCLUDE_SCATTER_PHIDGETS_SCATTER_PHIDGETS_H_ */

My utest.cpp looks like this:

#include "scatter_phidgets/scatter_phidgets.h"
#include "gtest/gtest.h"


TEST(TestScatterPhidgets, updatesInputQueueForInvertedLowState)
{
    digital_input testInput;
    testInput.low_state = 1;
    int testint = 0;
    updateQueue(testInput, testint);
    EXPECT_EQ(testInput.sum, 1);
}

int main(int argc, char **argv){
  testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}

Here's my issue: my package builds fine with catkin_make, however catkin_make tests fails with the following error:

[100%] Building CXX object scatter_phidgets/CMakeFiles/utest.dir/test/utest.cpp.o
Linking CXX executable /home/joe/test_catkin_ws/devel/lib/scatter_phidgets/utest
CMakeFiles/utest.dir/test/utest.cpp.o: In function `TestScatterPhidgets_updatesInputQueueForInvertedLowState_Test::TestBody()':
utest.cpp:(.text+0x62): undefined reference to `updateQueue(digital_input, int)'
collect2: error: ld returned 1 exit status
make[3]: *** [/home/joe/test_catkin_ws/devel/lib/scatter_phidgets/utest] Error 1
make[2]: *** [scatter_phidgets/CMakeFiles/utest.dir/all] Error 2
make[1]: *** [CMakeFiles/tests.dir/rule] Error 2
make: *** [tests] Error 2
Invoking "make tests -j8 -l8" failed

Now I really hope that I am making some simple mistake, however I cannot for the life of me get this thing to find that function.

What I have tried: At first I thought it simply wasn't finding the header file, however if I comment out the function call it does not complain about me using the struct that is defined in the header file.

Can anyone shed some light on what I am doing wrong? (or even better, point me in the direction of a simplest compiling example of a ros package using gtest to perform unit tests on functions that are not within the same file as the unit tests themselves, such is the case in many examples I have seen)

Thanks, Joe

Update 10/09 6:40pm est Not that I think it will make a difference, but today I converted things over to catkin build from catkin_make, it does not seem to have had any effect though (not that I was expecting it to).

Does anyone have an example of a package that successfully builds and runs gtest unit tests on functions defined in a separate header file, all of this being for ROS of course?

Update 10/09 7:33pm est Removed the printout from part of the last update since it was due to an unrelated omission, my fault!

Originally posted by jgilsenan on ROS Answers with karma: 181 on 2016-10-06

Post score: 1

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So I figured out what was wrong, and I suppose that most of you out there would consider this a "beginner's mistake" however due to some reasons I will explain below, I think that this can be considered an "answer":

The answer to my issue was sort-of provided in this answer and later sort-of-but-closer-to provided in this other answer however in my lacking of a thorough understanding of CMake, gtest, catkin, etc, I missed a crucial detail which lead me to a lot of frustration. I say "sort-of" in these cases because, although they are correct, they do not help users who, say, don't simply need a reminder that they already knew the answer. Since I can't imagine that I am the only one out there who will ever find themselves in such a position, and since this ROS documentation for gtest is practically useless for anyone who doesn't already know everything they need to know about linking, I feel it necessary to explain why I had the above-described issue and how I solved it. (in my defense, I am a self-taught Mech E pretending to be a software engineer, which is to be read: if it's something I ought to know, I probably don't know it yet).

Leading up to writing the code that caused me so much pain, I had very little experience in proper unit testing save for some tutorials that I had followed which went smoothly and were simple. As a result I overlooked the fact that the test code for the tutorials was all in the form of libraries, and my above-posted snippets show that in the form of me trying to test a library that did not exist. My lack of understanding lead me to believe that all I had to do was include the header for the code that I wanted to test and everything would be hunky dory, I was wrong.

If you are having similar problems as me, check if the code you want to test is even available as a library to the test code.

I remedied this by adding the following to my CMakelists after the catkin_package() section and before the include_directories() section:

add_library(scatter_phidgets
    src/scatter_phidgets.cpp)
target_link_libraries(scatter_phidgets ${catkin_LIBRARIES})

Furthermore, and as mentioned in this answer and this other answer, you have to link your test executable against the library you create above. Although I admit I am still not 100% on what the background mechanics of the linking are, for me this consisted of changing this:

if (CATKIN_ENABLE_TESTING)
  catkin_add_gtest(utest test/utest.cpp)
  target_link_libraries(utest ${catkin_LIBRARIES})
endif()

And modifying it so that it looks like this:

if (CATKIN_ENABLE_TESTING)
  catkin_add_gtest(utest test/utest.cpp)
  target_link_libraries(utest ${catkin_LIBRARIES} scatter_phidgets)
endif()

After doing so catkin_make run_tests and catkin run_tests (now I am using catkin_tools I guess) not only successfully built my tests, but showed me that I had placed some unnecessary code in the function I was trying to test by failing the test! (which I considered a huge success, here's to TDD!)

Additional reasons why this should be allowed as an answer:

  1. Because the gtest ROS page completely leaves this out, assumes that you already know much of this, and fails to provide a simplest working example.
  2. Because you can write an entire ROS package to do whatever you want, and it will be successful and build and solve world hunger and tie your shoes for you but it won't warn you that if you want to test the slew of ROS-agnostic functions you are bound to write, that you need them in a library.

Originally posted by jgilsenan with karma: 181 on 2016-10-09

This answer was ACCEPTED on the original site

Post score: 5

Original comments

Comment by jgilsenan on 2016-10-09:
I apologize if I am somehow wrong here, I am relatively new at this, and since it took a lot of skimming through existing ROS code bases to find the correlation between the library thing and the testing thing, I may be making some assumptions based on the conclusions I drew.

Comment by jgilsenan on 2016-10-09:
Please gently correct me as needed!

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