Add flags to link against test fixture

[osrf-migration]

Original report (archived issue) by Nate Koenig (Bitbucket: Nathan Koenig).

---

Should we modify gazebo's cmake config to include the test fixture? See pull request #1818.

[osrf-migration]

Original comment by Carlos Agüero (Bitbucket: caguero, GitHub: caguero).

---

Summary after some discussion with @nkoenig:

• Advantages: Easy to use for the users.
• Disadvantages: By default we would include in the GAZEBO_LIBRARIES a library that is not strictly necessary for running Gazebo. However, linkers are pretty smart and they don't include a library if it's not really needed except that in our case libgazebo_server_fixture is a static library. This might negatively affect every plugin or test that links with ${GAZEBO_LIBRARIES}.

Potential solutions:

• Learn why libgazebo_server_fixture is static. This might negatively affect the time required to link an integration tests. This issue might be related. If possible, make libgazebo_server fixture a dynamic library.

• Use an optional list of components when doing find_package(gazebo)

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

As I said in the pull request, I'm linking specifically against gazebo_test_fixture in the benchmark repository. I think the extra work for downstream users in creating integration tests is not just linking against gazebo_test_fixture; that part is easy. There's lots of steps, though, that could be simplified:

• add gtest sources to downstream repository
• compile gtest
• for each test, create an executable, link against relevant libraries
• add the test
• create a check_test_ran test to catch seg-faults

We use some cmake macros to simplify this for ourselves. Would it be desirable to install a cmake helper macro/function intended for downstream use (similar to osrf/gazebo/cmake/GazeboTestUtils.cmake or the TestMacro.cmake in the benchmark repository)? I would ask the opinion of @dirk-thomas if we were to do so.

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

---

We should scope the goal of this issue. Is it

1. Make a public facing mechanism to link against the test fixture, and leave the rest of the compilation details up to the user, or
2. Create an installable cmake helper for using gazebo's test fixture?

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

---

• set version to "all"