Add test cases

[130s]

Test for GUI is hard but non-GUI functions can be easily tested.

• Number of included { launch files, nodes } are as intended.
  • For me this is important because I'm seeing with a launch file with 4 included launches, there are only 2 launches on rqt_launchtree. I'm digging the issue and I can't disclose an info since this is private pkg.

Will keep adding more ideas whenever I have more.

[130s]

For me this is important because I'm seeing with a launch file with 4 included launches, there are only 2 launches on rqt_launchtree. I'm digging the issue and I can't disclose an info since this is private pkg.

NVM. This issue comes from lower than rqt_launchtree. I found that with roslaunch --nodes xxxx.launch the returned nodes are fewer already.